Science.gov

Sample records for 14-fr peel-away sheath

  1. Abduction of Arm Facilitates Correction of Kinked Peel-Away Sheath During Subclavian Central Line Placement.

    PubMed

    Kim, Sunghoon

    2015-12-01

    A tunneled central line catheter placement using a subclavian vein approach can be complicated by an occurrence of peel-away sheath kink which prevents the advancement of the catheter through the sheath. The kink is created due to the angular junction of subclavian and brachiocephalic veins which meet at 90 degree angle. A technique is described which corrects the peel-away sheath kink by extending the subclavian/brachiocephalic vein angle to greater than 90 degrees by abducting the patient's arm.

  2. Elkmont Vehicle Bridge, Construction PeelAway Great Smoky Mountains National ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Elkmont Vehicle Bridge, Construction Peel-Away - Great Smoky Mountains National Park Roads & Bridges, Elkmont Vehicle Bridge, Spanning Little River at Elkmont Campground, Gatlinburg, Sevier County, TN

  3. NICMOS PEELS AWAY LAYERS OF DUST TO SHOW INNER REGION OF DUSTY NEBULA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The revived Near Infrared Camera and Multi-Object Spectrometer (NICMOS) aboard NASA's Hubble Space Telescope has penetrated layers of dust in a star-forming cloud to uncover a dense, craggy edifice of dust and gas . This region is called the Cone Nebula (NGC 2264), so named because, in ground-based images, it has a conical shape. NICMOS enables the Hubble telescope to see in near-infrared wavelengths of light, so that it can penetrate the dust that obscures the nebula's inner regions. But the Cone is so dense that even the near-infared 'eyes' of NICMOS can't penetrate all the way through it. The image shows the upper 0.5 light-years of the nebula. The entire nebula is 7 light-years long. The Cone resides in a turbulent star-forming region, located 2,500 light-years away in the constellation Monoceros. Radiation from hot, young stars [located beyond the top of the image] has slowly eroded the nebula over millions of years. Ultraviolet light heats the edges of the dark cloud, releasing gas into the relatively empty region of surrounding space. NICMOS has peeled away the outer layers of dust to reveal even denser dust. The denser regions give the nebula a more three-dimensional structure than can be seen in the visible-light picture at left, taken by the Advanced Camera for Surveys aboard the Hubble telescope. In peering through the dusty facade to the nebula's inner regions, NICMOS has unmasked several stars [yellow dots at upper right]. Astronomers don't know whether these stars are behind the dusty nebula or embedded in it. The four bright stars lined up on the left are in front of the nebula. The human eye cannot see infrared light, so colors have been assigned to correspond with near-infrared wavelengths. The blue light represents shorter near-infrared wavelengths and the red light corresponds to longer wavelengths. The NICMOS color composite image was made by combining photographs taken in J-band, H-band, and Paschen-alpha filters. The NICMOS images were taken

  4. Communication through plasma sheaths

    SciTech Connect

    Korotkevich, A. O.; Newell, A. C.; Zakharov, V. E.

    2007-10-15

    We wish to transmit messages to and from a hypersonic vehicle around which a plasma sheath has formed. For long distance transmission, the signal carrying these messages must be necessarily low frequency, typically 2 GHz, to which the plasma sheath is opaque. The idea is to use the plasma properties to make the plasma sheath appear transparent.

  5. No Pixel Left Behind - Peeling Away NASA's Satellite Swaths

    NASA Astrophysics Data System (ADS)

    Cechini, M. F.; Boller, R. A.; Schmaltz, J. E.; Roberts, J. T.; Alarcon, C.; Huang, T.; McGann, M.; Murphy, K. J.

    2014-12-01

    Discovery and identification of Earth Science products should not be the majority effort of scientific research. Search aides based on text metadata go to great lengths to simplify this process. However, the process is still cumbersome and requires too much data download and analysis to down select to valid products. The EOSDIS Global Imagery Browse Services (GIBS) is attempting to improve this process by providing "visual metadata" in the form of full-resolution visualizations representing geophysical parameters taken directly fromt he data. Through the use of accompanying interpretive information such as color legends and the natural visual processing of the human eye, researchers are able to search and filter through data products in a more natural and efficient way. The GIBS "visual metadata" products are generated as representations of Level 3 data or as temporal composites of the Level 2 granule- or swath-based data products projected across a geographic or polar region. Such an approach allows for low-latency tiled access to pre-generated imagery products. For many GIBS users, the resulting image suffices for a basic representation of the underlying data. However, composite imagery presents an insurmountable problem: for areas of spatial overlap within the composite, only one observation is visually represented. This is especially problematic in the polar regions where a significant portion of sensed data is "lost." In response to its user community, the GIBS team coordinated with its stakeholders to begin developing an approach to ensure that there is "no pixel left behind." In this presentation we will discuss the use cases and requirements guiding our efforts, considerations regarding standards compliance and interoperability, and near term goals. We will also discuss opportunities to actively engage with the GIBS team on this topic to continually improve our services.

  6. Peeling Away Timing Error in NetFlow Data

    NASA Astrophysics Data System (ADS)

    Trammell, Brian; Tellenbach, Bernhard; Schatzmann, Dominik; Burkhart, Martin

    In this paper, we characterize, quantify, and correct timing errors introduced into network flow data by collection and export via Cisco NetFlow version 9. We find that while some of these sources of error (clock skew, export delay) are generally implementation-dependent and known in the literature, there is an additional cyclic error of up to one second that is inherent to the design of the export protocol. We present a method for correcting this cyclic error in the presence of clock skew and export delay. In an evaluation using traffic with known timing collected from a national-scale network, we show that this method can successfully correct the cyclic error. However, there can also be other implementation-specific errors for which insufficient information remains for correction. On the routers we have deployed in our network, this limits the accuracy to about 70ms, reinforcing the point that implementation matters when conducting research on network measurement data.

  7. Sheath energy transmission in a collisional plasma with collisionless sheath

    SciTech Connect

    Tang, Xian-Zhu Guo, Zehua

    2015-10-15

    Sheath energy transmission governs the plasma energy exhaust onto a material surface. The ion channel is dominated by convection, but the electron channel has a significant thermal conduction component, which is dominated by the Knudsen layer effect in the presence of an absorbing wall. First-principle kinetic simulations reveal a robustly supersonic sheath entry flow. The ion sheath energy transmission and the sheath potential are accurately predicted by a sheath model of truncated bi-Maxwellian electron distribution. The electron energy transmission is further enhanced by a parallel heat flux of the perpendicular degrees of freedom.

  8. 21 CFR 884.5320 - Glans sheath.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... sheath. (a) Identification. A glans sheath device is a sheath which covers only the glans penis or part... the entire shaft of the penis. It is indicated only for the prevention of pregnancy and not for the...

  9. 21 CFR 884.5320 - Glans sheath.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... sheath. (a) Identification. A glans sheath device is a sheath which covers only the glans penis or part... the entire shaft of the penis. It is indicated only for the prevention of pregnancy and not for the...

  10. Sheaths: A Comparison of Magnetospheric, ICME, and Heliospheric Sheaths

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Richardson, J. D.; Liu, W.

    2007-01-01

    When a supersonic flow encounters an obstacles, shocks form to divert the flow around the obstacle. The region between the shock and the obstacle is the sheath, where the supersonic flow is compressed, heated, decelerated, and deflected. Supersonic flows, obstacles, and thus sheaths are observed on many scales throughout the Universe. We compare three examples seen in the heliosphere, illustrating the interaction of the solar wind with obstacles of three very different scales lengths. Magnetosheaths form behind planetary bow shocks on scales ranging from tens to 100 planetary radii. ICME sheath form behind shocks driven by solar disturbances on scale lengths of a few to tens of AU. The heliosheath forms behind the termination shock due to the obstacle presented by the interstellar medium on scale lengths of tens to a hundred AU. Despite this range in scales some common features have been observed. Magnetic holes, possibly due to mirror mode waves, have been observed in all three of these sheaths. Plasma depletion layers are observed in planetary and ICME sheaths. Other features observed in some sheaths are wave activity (ion cyclotron, plasma), energetic particles, transmission of Alfven waves/shocks, tangential discontinuities turbulence behind quasi-parallel shocks, standing slow mode waves, and reconnection on the obstacle boundary. We compare these sheath regions, discussing similarities and differences and how these may relate to the scale lengths of these regions.

  11. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, J.R.

    1987-05-15

    A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

  12. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R.

    1987-12-01

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  13. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R.

    1987-12-01

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  14. Snare sheath versus evolution sheath in transvenous lead extraction.

    PubMed

    Kong, Jihua; Tian, Yilun; Guo, Fei; Ze, Feng; Duan, Jiangbo; Wang, Long; Li, Xuebin; Guo, Jihong

    2015-01-01

    Lead extraction remains a challenging procedure with significant success. Owing to the increasing use of cardiac implantable electronic devices, there is a growing need for effective techniques management, to avoid the occurrence of device-related complications and lead dysfunction. We made a comparison of Evolution sheath and Needles Eye Snare sheath (abbreviated to Snare sheath) by analyzed the results using two kind of the methods in the Cardiology Center of Peking University People's Hospital. In the retrospective study we evaluated patients who underwent lead extraction from July 2013 to July 2014. Those who underwent lead removal without using evolution or snare were excluded. Primary endpoints included total exposure time, operation time, and complications. Data on clinical characteristics, indications, and outcomes were prospectively collected and analyzed. A total of 76 patients were included in the study (65.8% male; aged 68.1±14.34 years old). Snare and Evolution were used in 59 and 17 patients, respectively. A total of 134 leads were removed with 103 leads (76.87%) extracted using the Snare sheath. Lead age was 10.8±7.0 years. Complete extraction was observed in 67 patients of 124 leads. Evolution sheath was associated with significantly lower complication even after adjustment of the number of leads, type of leads, and lead age, compared to the Snare group (P<0.05). In the Snare sheath group, mortality rate was 1.69% and minor complication rate was 3.39%. When compared to the Snare sheath, lead extraction with the Evolution sheath has less X-ray exposure time and less operation time (P<0.05), while with a higher success rate (P<0.05). Besides, the Evolution group has fewer major and minor complications.

  15. Optic Nerve Sheath Meningiomas.

    PubMed

    Radhakrishnan, Sunita; Lee, Michael S

    2005-01-01

    Optic nerve sheath meningiomas (ONSMs) grow slowly and, if untreated, patients may have stable visual function for up to several years. Treatment of an ONSM may lead to vision loss (radiation retinopathy or optic neuropathy). Therefore, observation is recommended for a patient with ONSM and relatively preserved visual acuity, color vision, pupils, and visual fields. Follow-up every 4 to 6 months initially is recommended extending to annual examinations if visual function and tumor size remain stable for a few years. Neuroimaging can be repeated every 12 months. An undisputed decline in visual function or any intracranial extension warrants treatment of the ONSM. The treatment of choice for a tumor confined to the orbit is stereotactic fractionated radiation. Stereotactic fractionated radiation uses multiple small doses of radiation using tight margins. A reasonable alternative, three-dimensional conformal fractionated radiation uses computed tomography-guided planning but usually requires wider margins. Conventional radiation uses much wider margins and would not be recommended for treatment of ONSM. The radiation can be administered during 5 to 6 weeks in 28 daily fractions of 1.8 to 2 Gy/fraction to a total of 50.4 to 56 Gy. Many patients have improvement or stabilization of their visual function. Gamma knife radiosurgery does not have a role in ONSM because the required dose is toxic to the optic nerve. A tumor that extends intracranially may be treated with fractionated radiation if any vision remains. Surgical excision can be considered for significant intracranial extension but this often leads to complete vision loss in the ipsilateral eye. A blind, disfigured eye also may be treated with en bloc surgical resection of the meningioma.

  16. Dust in the magnetized sheath

    SciTech Connect

    Pandey, B. P.; Samarian, A.; Vladimirov, S. V.

    2007-09-15

    In the present work the structure of the magnetized sheath is investigated in the multifluid framework. The ambient magnetic field is assumed parallel to the wall and the effect of the plasma magnetization, plasma ionization, and plasma-neutral collisions on the sheath is examined. It is shown that the width of the non-neutral boundary layer is dependent on the collision frequencies as well as on the plasma magnetization. The size of the sheath layer can decrease with the increase in magnetic field. The increase in the ion-neutral collision can also adversely affect the sheath size. The equilibrium and levitation of the dust particles in a collisional magnetized sheath are shown to depend on the collision frequencies and on the magnetization. Further, the increase in the collision or magnetization invariably leads to the presence of the positively charged grains near the plasma wall suggesting that the grain levitation inside the charged layer is implicitly dependent on the plasma parameters in a nontrivial way.

  17. Progress on Quantitative Modeling of rf Sheaths

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.; Kohno, H.; Wright, J. C.

    2011-12-01

    A new quantitative approach for computing the rf sheath potential is described, which incorporates plasma dielectric effects and the relative geometry of the magnetic field and the material boundaries. The new approach uses a modified boundary condition ("rf sheath BC") that couples the rf waves and the sheaths at the boundary. It treats the sheath as a thin vacuum region and matches the fields across the plasma-vacuum boundary. When combined with the Child-Langmuir Law (relating the sheath width and sheath potential), the model permits a self-consistent determination of the sheath parameters and the rf electric field at the sheath-plasma boundary. Semi-analytic models using this BC predict a number of general features, including a sheath voltage threshold, a dimensionless parameter characterizing rf sheath effects, and the existence of sheath plasma waves with an associated resonance. Since the sheath BC is nonlinear and dependent on geometry, computing the sheath potential numerically is a challenging computational problem. Numerical results will be presented from a new parallel-processing finite-element rf wave code for the tokamak scrape-off layer (called "rfSOL"). The code has verified the physics predicted by analytic theory in 1D, and extended the solutions into model 2D geometries. The numerical calculations confirm the existence of multiple roots and hysteresis effects, and parameter studies have been carried out. Areas for future work will be discussed.

  18. Sheath-in-Sheath Technique for Exteriorization of Body Floss Wire.

    PubMed

    Pua, Uei

    2017-05-01

    In this technique, we describe the insertion of a second sheath into the primary sheath containing a guidewire that is meant to be exteriorized. The second sheath serves to open the valve of the primary sheath and creates a water-tight chamber for the guidewire to enter. The second sheath is then removed, exposing the successfully exteriorized guidewire. This technique is an useful adjunct to conventional guidewire exteriorization techniques during body floss procedures. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Generalized sheath criterion for arbitrary degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.

    2017-01-01

    In this research, we study the generalized sheath criterion for plasmas with an arbitrary degree of electron degeneracy and temperature, ranging from the classical dilute regime to the fully degenerate quantum plasmas. The latter may be relevant to warm dense matter and/or laboratory high energy density matter or even astrophysical stellar plasmas. The hydrostatic one dimensional model is used to establish the generalized Bohm's criterion for sheath entrance ion speed limits, and the small amplitude theory of the sheath problem, which accurately describes the sheath parameters for lower ion acoustic Mach numbers, is developed. Our results indicate that the sheath characteristic parameters such as electrostatic potential and density profiles, as well as the wall potential and the sheath length, are significantly affected by plasma parameters such as the ion and electron temperature and number densities in the plasma region. In particular, there are fundamental differences between sheath structures of the dilute classical plasmas and those of dense quantum ones.

  20. Water in the formation of biogenic minerals: peeling away the hydration layers.

    PubMed

    Dorvee, Jason R; Veis, Arthur

    2013-08-01

    Minerals of biogenic origin form and crystallize from aqueous environments at ambient temperatures and pressures. The in vivo environment either intracellular or intercellular, contains many components that modulate both the activity of the ions which associate to form the mineral, as well as the activity and structure of the crowded water. Most of the studies about the mechanism of mineralization, that is, the detailed pathways by which the mineral ions proceed from solution to crystal state, have been carried out in relatively dilute solutions and clean solutions. These studies have considered both thermodynamic and kinetic controls. Most have not considered the water itself. Is the water a passive bystander, or is it intimately a participant in the mineral ion densification reaction? A wide range of experiments show that the mineralization pathways proceed through a series of densification stages with intermediates, such as a "dense liquid" phase and the prenucleation clusters that form within it. This is in contrast to the idea of a single step phase transition, but consistent with the Gibbs concept of discontinuous phase transitions from supersaturated mother liquor to crystal. Further changes in the water structure at every surface and interface during densification guides the free energy trajectory leading to the crystalline state. In vertebrates, mineralization takes place in a hydrated collagen matrix, thus water must be considered as a direct participant. Although different in detail, the crystallization of calcium phosphates, as apatite, and calcium carbonates, as calcite, are mechanistically identical from the viewpoint of water. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Aluminum Wire Rope Polyethylene Sheathing Failure.

    DTIC Science & Technology

    1997-12-01

    of polyethylene taken from sheathed wire rope samples with and without cracking . Sample Melting Point (°C) Heat of Fusion (J/g) Percent...The cracked polyethylene sheathing was made from a higher density PE than the uncracked sheathing. It failed when it was wound onto a cable reel...12, 512 (1979). 6. A. Lustiger, ’ Environmental Stress Cracking : The Phenomenon and its Utility’, Chapter 16 in Failure of Plastics, edited by W

  2. Ureteral access strategies: pro-access sheath.

    PubMed

    Vanlangendonck, Richard; Landman, Jaime

    2004-02-01

    Routine use of the ureteral access sheath during flexible ureteroscopic procedures provides consistent, reliable, and unencumbered access to the upper tracts. The ureteral access sheath can be reliably and easily deployed if used properly and requires no special training. As such, it can be easily adopted into current urologic practice. Not only does the access sheath facilitate rapid, repeated, and atraumatic access to the upper tracts, but it also avoids back-loading over a superstiff guidewire, which may incur costly damage to the ureteroscope. The access sheath reduces overall costs and decreases operative times. Furthermore, application of a ureteral access sheath reduces the frustration associated with complex and some routine ureteroscopic procedures by optimizing irrigant flow to improve the surgeon's endoscopic vision while minimizing the intrarenal pressures that the kidney must tolerate. There is no evidence that the access sheath results in clinically significant ureteral ischemia, and extensive clinical use of the access sheath for long procedures has not resulted in increased stricture formation. Finally, the ureteral access sheath is useful for other procedures, such as PCNL, by improving visualization and minimizing the requirement for multiple percutaneous access sites. Winston Churchill said it best: "Give us the tools and we will finish the job." Industry has provided urologists with the tools in the form of advanced flexible ureteroscopes, the holmium laser, nitinol baskets, and the ureteral access sheath. Now it is up to urologists to finish the job.

  3. Transient sheath overvoltages in armored power cables

    SciTech Connect

    Gustavsen, B.; Sletbak, J.

    1996-07-01

    This paper is concerned with methods of limiting the build-up of transient voltages between sheath and armor in long armored power cables. Calculations by a frequency dependent cable model demonstrate that this voltage can be efficiently limited to an acceptable level by introducing sheath-armor bondings at regular intervals, or by using a semiconductive sheath-armor interlayer. The paper investigates the required minimum length between bondings, as well as the required conductivity of the sheath-armor interlayer if the use of bondings is to be avoided.

  4. Gold ink coating of thermocouple sheaths

    DOEpatents

    Ruhl, H. Kenneth

    1992-01-01

    A method is provided for applying a gold ink coating to a thermocouple sheath which includes the steps of electropolishing and oxidizing the surface of the thermocouple sheath, then dipping the sheath into liquid gold ink, and finally heat curing the coating. The gold coating applied in this manner is highly reflective and does not degrade when used for an extended period of time in an environment having a temperature over 1000.degree. F. Depending on the application, a portion of the gold coating covering the tip of the thermocouple sheath is removed by abrasion.

  5. A Randomized Study of Minimally Invasive Percutaneous Nephrolithotomy (MPCNL) with the aid of a patented suctioning sheath in the treatment of renal calculus complicated by pyonephrosis by one surgery.

    PubMed

    Huang, Jianrong; Song, Leming; Xie, Donghua; Li, Monong; Deng, Xiaolin; Hu, Min; Peng, Zuofeng; Liu, Tairong; Du, Chuance; Yao, Lei; Liu, Shengfeng; Guo, Shulin; Zhong, Jiuqing

    2016-12-08

    Calculus pyonephrosis is difficult to manage. The aim of this study is to explore the value of a patented suctioning sheath assisted minimally invasive percutaneous nephrolithotomy (MPCNL) in the treatment of calculus pyonephrosis. One hundred and eighty two patients with calculus pyonephrosis were randomizely divided into observation group (n = 91) and control group (n = 91). The control group was treated with MPCNL traditionally using peel-away sheath while the observation group was treated with MPCNL using the patented suctioning sheath. All the patients in the observation group underwent one stage surgical treatment, 14 patients in the control group underwent first-stage surgery with the rest of the group underwent one stage surgery. The complication rate was 12.1% in the observation group, significantly lower than the rate in the control group which was 51.6%; One surgery stone clearance in the observation group was 96.7% while it was 73.6% in the control group; operative time in the observation group was (54.5 ± 14.5) min, compared to (70.2 ± 11.7) min in the control group; the bleeding amount in the observation group was (126.4 ± 47.2) ml, compared to (321.6 ± 82.5) ml in the control group; the hospitalization duration for the observation group was (6.4 ± 2.3) days, compared to (10.6 ± 3.7) days in the control group. Comparison of the above indicators, the observation group was better than the control group with significant difference (p < 0.001 each). Minimally invasive percutaneous nephrolithotomy with the aid of the patented suctioning sheath in the treatment of calculus pyonephrosis in one surgery is economic, practical, and warrants clinical promotion. This study was registered with Chinese Clinical Trial Registry on May 18, 2016 (retrospective registration) with a trial registration number of ChiCTR-IOR-16008490 .

  6. Theory of the electron sheath and presheath

    SciTech Connect

    Scheiner, Brett; Baalrud, Scott D.; Yee, Benjamin T.; Hopkins, Matthew M.; Barnat, Edward V.

    2015-12-30

    Here, electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in particle-in-cell(PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperature plasma conditions (Te >> Ti), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under common plasma conditions, the electron presheath extends much further into the plasma than an analogous ion presheath. PIC simulations reveal that the ion density in the electron presheath is determined by a flow around the electron sheath and that this flow is due to 2D aspects of the sheath geometry. Simulations also indicate the presence of ion acoustic instabilities excited by the differential flow between electrons and ions in the presheath, which result in sheath edge fluctuations. The 1D model and time averaged PIC simulations are compared and it is shown that the model provides a good description of the electron sheath and presheath.

  7. Theory of the electron sheath and presheath

    DOE PAGES

    Scheiner, Brett; Baalrud, Scott D.; Yee, Benjamin T.; ...

    2015-12-30

    Here, electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in particle-in-cell(PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperaturemore » plasma conditions (Te >> Ti), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under common plasma conditions, the electron presheath extends much further into the plasma than an analogous ion presheath. PIC simulations reveal that the ion density in the electron presheath is determined by a flow around the electron sheath and that this flow is due to 2D aspects of the sheath geometry. Simulations also indicate the presence of ion acoustic instabilities excited by the differential flow between electrons and ions in the presheath, which result in sheath edge fluctuations. The 1D model and time averaged PIC simulations are compared and it is shown that the model provides a good description of the electron sheath and presheath.« less

  8. Rectus sheath abscess after laparoscopic appendicectomy

    PubMed Central

    Golash, Vishwanath

    2007-01-01

    Port site wound infection, abdominal wall hematoma and intraabdominal abscess formation has been reported after laparoscopic appendicectomy. We describe here a rectus sheath abscess which occurred three weeks after the laparoscopic appendicectomy. It was most likely the result of secondary infection of the rectus sheath hematoma due to bleeding into the rectus sheath from damage to the inferior epigastric arteries or a direct tear of the rectus muscle. As far as we are aware this complication has not been reported after laparoscopic appendicectomy. PMID:21124654

  9. Side-welded fast response sheathed thermocouple

    DOEpatents

    Carr, Kenneth R.

    1981-01-01

    A method of fabricating the measuring junction of a grounded-junction sheathed thermocouple to obtain fast time response and good thermal cycling performance is provided. Slots are tooled or machined into the sheath wall at the measuring junction, the thermocouple wires are laser-welded into the slots. A thin metal closure cap is then laser-welded over the end of the sheath. Compared to a conventional grounded-junction thermocouple, the response time is 4-5 times faster and the thermal shock and cycling capabilities are substantially improved.

  10. Side-welded fast response sheathed thermocouple

    DOEpatents

    Carr, K.R.

    A method of fabricating the measuring junction of a grounded-junction sheathed thermocouple to obtain fast time response and good thermal cycling performance is provided. Slots are tooled or machined into the sheath wall at the measuring junction, the thermocouple wires are laser-welded into the slots. A thin metal closure cap is then laser-welded over the end of the sheath. Compared to a conventional grounded-junction thermocouple, the response time is 4 to 5 times faster and the thermal shock and cycling capabilities are substantially improved.

  11. Effects of electron emission on sheath potential

    NASA Astrophysics Data System (ADS)

    Dow, Ansel; Khrabrov, Alexander; Kaganovich, Igor; Schamis, Hanna

    2015-11-01

    We investigate the potential profile of a sheath under the influence of surface electron emission. The plasma and sheath profiles are simulated using the Large Scale Plasma (LSP) particle-in-cell code. Using one dimensional models we corroborate the analytical relationship between sheath potential and plasma electron and emitted electron temperatures derived earlier. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.

  12. Rectus sheath hematoma: three case reports

    PubMed Central

    Kapan, Selin; Turhan, Ahmet N; Alis, Halil; Kalayci, Mustafa U; Hatipoglu, Sinan; Yigitbas, Hakan; Aygun, Ersan

    2008-01-01

    Introduction Rectus sheath hematoma is an uncommon cause of acute abdominal pain. It is an accumulation of blood in the sheath of the rectus abdominis, secondary to rupture of an epigastric vessel or muscle tear. It could occur spontaneously or after trauma. They are usually located infraumblically and often misdiagnosed as acute abdomen, inflammatory diseases or tumours of the abdomen. Case presentation We reported three cases of rectus sheath hematoma presenting with a mass in the abdomen and diagnosed by computerized tomography. The patients recovered uneventfully after bed rest, intravenous fluid replacement, blood transfusion and analgesic treatment. Conclusion Rectus sheath hematoma is a rarely seen pathology often misdiagnosed as acute abdomen that may lead to unnecessary laparotomies. Computerized tomography must be chosen for definitive diagnosis since ultrasonography is subject to error due to misinterpretation of the images. Main therapy is conservative management. PMID:18221529

  13. Intrasellar malignant peripheral nerve sheath tumor (MPNST).

    PubMed

    Krayenbühl, N; Heppner, F; Yonekawa, Y; Bernays, R L

    2007-02-01

    Intracranial malignant peripheral nerve sheath tumors (MPNST) and intrasellar schwannomas are rare tumors. We describe a case of an intrasellar schwannoma with progression to a MPNST, a finding that, although very rare, extends the differential diagnosis of intrasellar lesions.

  14. Carotid sheath haematoma: a case report.

    PubMed

    Yadav, Jayanthi; Badkur, D S; Arora, Arneet

    2009-10-01

    Carotid sheath haematoma is a rare finding, sometimes the only injury found in cases of manual strangulation without any associated external or internal injury to the neck. One such rare case is reported in an 8 year old female victim where presence of carotid sheath haematoma not only helped to ascertain the cause of death but also helped in the reconstruction of mechanism of infliction of force on the neck. 2009 Elsevier Ltd and Faculty of Forensic and Legal Medicine.

  15. Lipoma arborescens of the biceps tendon sheath.

    PubMed

    White, Eric A; Omid, Reza; Matcuk, George R; Domzalski, Jerome T; Fedenko, Alexander N; Gottsegen, Christopher J; Forrester, Deborah M; Patel, Dakshesh B

    2013-10-01

    Lipoma arborescens, described as lipomatous infiltration and distention of synovial villi resulting in a frond-like appearance, most frequently affects the suprapatellar recess of the knee. While there have been reports of this entity involving the upper extremity joints, bursa, and tendon sheaths, we present the first reported case of lipoma arborescens isolated to the biceps tendon sheath. We describe imaging and histologic findings with clinical correlation.

  16. Malignant Peripheral Nerve Sheath Tumors.

    PubMed

    Durbin, Adam D; Ki, Dong Hyuk; He, Shuning; Look, A Thomas

    2016-01-01

    Malignant peripheral nerve sheath tumors (MPNST) are tumors derived from Schwann cells or Schwann cell precursors. Although rare overall, the incidence of MPNST has increased with improved clinical management of patients with the neurofibromatosis type 1 (NF1) tumor predisposition syndrome. Unfortunately, current treatment modalities for MPNST are limited, with no targeted therapies available and poor efficacy of conventional radiation and chemotherapeutic regimens. Many murine and zebrafish models of MPNST have been developed, which have helped to elucidate the genes and pathways that are dysregulated in MPNST tumorigenesis, including the p53, and the RB1, PI3K-Akt-mTOR, RAS-ERK and Wnt signaling pathways. Preclinical results have suggested that new therapies, including mTOR and ERK inhibitors, may synergize with conventional chemotherapy in human tumors. The discovery of new genome editing technologies, like CRISPR-cas9, and their successful application to the zebrafish model will enable rapid progress in the faithful modeling of MPNST molecular pathogenesis. The zebrafish model is especially suited for high throughput screening of new targeted therapeutics as well as drugs approved for other purposes, which may help to bring enhanced treatment modalities into human clinical trials for this devastating disease.

  17. Dust particle dynamics in magnetized plasma sheath

    SciTech Connect

    Davoudabadi, M.; Mashayek, F.

    2005-07-15

    In this paper, the structure of a plasma sheath in the presence of an oblique magnetic field is investigated, and dynamics of a dust particle embedded in the sheath is elaborated. To simulate the sheath, a weakly collisional two-fluid model is implemented. For various magnitudes and directions of the magnetic field and chamber pressures, different plasma parameters including the electron and ion densities, ion flow velocity, and electric potential are calculated. A complete set of forces acting on the dust particle originating from the electric field in the sheath, the static magnetic field, gravity, and ion and neutral drags is taken into account. Through the trapping potential energy, the particle stable and unstable equilibria are studied while the particle is stationary inside the sheath. Other features such as the possibility of the dust levitation and trapping in the sheath, and the effect of the Lorentz force on the charged dust particle motion are also examined. An interesting feature is captured for the variation of the particle charge as a function of the magnetic field magnitude.

  18. Protective sheath for a continuous measurement thermocouple

    DOEpatents

    Phillippi, R.M.

    1991-12-03

    Disclosed is a protective thermocouple sheath of a magnesia graphite refractory material for use in continuous temperature measurements of molten metal in a metallurgical ladle and having a basic slag layer thereon. The sheath includes an elongated torpedo-shaped sheath body formed of a refractory composition and having an interior borehole extending axially therethrough and adapted to receive a thermocouple. The sheath body includes a lower end which is closed about the borehole and forms a narrow, tapered tip. The sheath body also includes a first body portion integral with the tapered tip and having a relatively constant cross section and providing a thin wall around the borehole. The sheath body also includes a second body portion having a relatively constant cross section larger than the cross section of the first body portion and providing a thicker wall around the borehole. The borehole terminates in an open end at the second body portion. The tapered tip is adapted to penetrate the slag layer and the thicker second body portion and its magnesia constituent material are adapted to withstand chemical attack thereon from the slag layer. The graphite constituent improves thermal conductivity of the refractory material and, thus, enhances the thermal responsiveness of the device. 4 figures.

  19. Protective sheath for a continuous measurement thermocouple

    DOEpatents

    Phillippi, R. Michael

    1991-01-01

    Disclosed is a protective thermocouple sheath of a magnesia graphite refractory material for use in continuous temperature measurements of molten metal in a metallurgical ladle and having a basic slag layer thereon. The sheath includes an elongated torpedo-shaped sheath body formed of a refractory composition and having an interior borehole extending axially therethrough and adapted to receive a thermocouple. The sheath body includes a lower end which is closed about the borehole and forms a narrow, tapered tip. The sheath body also includes a first body portion integral with the tapered tip and having a relatively constant cross section and providing a thin wall around the borehole. The sheath body also includes a second body portion having a relatively constant cross section larger than the cross section of the first body portion and providing a thicker wall around the borehole. The borehole terminates in an open end at the second body portion. The tapered tip is adapted to penetrate the slag layer and the thicker second body portion and its magnesia constituent material are adapted to withstand chemical attack thereon from the slag layer. The graphite constituent improves thermal conductivity of the refractory material and, thus, enhances the thermal responsiveness of the device.

  20. Protective sheath for a continuous measurement thermocouple

    SciTech Connect

    Phillippi, R.M.

    1991-12-03

    Disclosed is a protective thermocouple sheath of a magnesia graphite refractory material for use in continuous temperature measurements of molten metal in a metallurgical ladle and having a basic slag layer thereon. The sheath includes an elongated torpedo-shaped sheath body formed of a refractory composition and having an interior borehole extending axially therethrough and adapted to receive a thermocouple. The sheath body includes a lower end which is closed about the borehole and forms a narrow, tapered tip. The sheath body also includes a first body portion integral with the tapered tip and having a relatively constant cross section and providing a thin wall around the borehole. The sheath body also includes a second body portion having a relatively constant cross section larger than the cross section of the first body portion and providing a thicker wall around the borehole. The borehole terminates in an open end at the second body portion. The tapered tip is adapted to penetrate the slag layer and the thicker second body portion and its magnesia constituent material are adapted to withstand chemical attack thereon from the slag layer. The graphite constituent improves thermal conductivity of the refractory material and, thus, enhances the thermal responsiveness of the device. 4 figures.

  1. How to Patch Active Plasma and Collisionless Sheath: Practical Guide

    SciTech Connect

    Kaganovich, Igor D.

    2002-08-22

    Most plasmas have a very thin sheath compared with the plasma dimension. This necessitates separate calculations of the plasma and sheath. The Bohm criterion provides the boundary condition for calculation of plasma profiles. To calculate sheath properties, a value of electric field at the plasma-sheath interface has to be specified in addition to the Bohm criterion. The value of the boundary electric field and robust procedure to approximately patch plasma and collisionless sheath with a very good accuracy are reported.

  2. Are sheath folds late stage flanking structures?

    NASA Astrophysics Data System (ADS)

    Reber, Jacqueline E.; Dabrowski, Marcin; Schmid, Daniel W.

    2010-05-01

    Sheath folds can be described as highly non-cylindrical folds or as cone shaped with a rounded apex. A cross section of a sheath fold perpendicular to its elongation direction shows usually an elliptical shape. Sheath folds can be observed in nature within a wide range of materials and across many orders of size magnitude. A classification scheme has been developed by Alsop and Holdsworth (Journal of Structural Geology, 2006) which divides sheath folds into different categories depending on the ratio of the aspect ratio of the innermost and outermost "ring". Different initial conditions such as rigid objects and precursor folds formed through buckling were suggested as a trigger for the development of sheath folds. However, in nature sheath folds can also be observed where no rigid objects or precursor folds can be seen. In such cases we propose weak objects or zones as possible activators. According to this approach sheath folds represent a late stage of flanking structures. To simulate the weak zone we use an infinitely weak elliptical inclusion embedded in a homogeneous matrix. Planar markers such as bedding or foliation make the sheath geometry visible. To test the impact of the initial shape of the weak zone on the formation of the sheath folds the aspect ratio of the slip ellipse is changed systematically. As the geometry of sheath folds is truly three dimensional we use a 3D analytical model to investigate their formation. The model is based on an adapted internal and external Eshelby solution (Eshelby, Proceedings of the Royal Society of London series a-Mathematical and Physical Sciences, 1957 and 1959) for viscous rheologies and elliptical inclusions described in Exner and Dabrowski (Journal of Structural Geology, 2010 (submitted)). The ellipse as well as the matrix has linear viscous, isotropic, incompressible material properties. To analyze the cross-section the calculated folds are cut perpendicular to the simple shear stretching direction while the

  3. Attic construction with sheathing-applied insulation

    SciTech Connect

    Rose, W.B.

    1995-12-31

    Two years of study at a building research laboratory have been applied to cathedralized residential attic construction. Cathedralized attics are rafter-framed or truss-framed attics with flat ceilings in which the insulation is placed against the underside of the roof sheathing rather than on top of the ceiling drywall. The potential benefits of sheathing-applied insulation are considerable and are due to the fact that the attic space becomes part of the conditioned volume. Concern is often expressed that moisture damage may occur in the sheathing. The intent of the current study was to address those concerns. This study allowed an assessment of the performance of cathedralized ceilings, given the following construction variables: (1) ventilation vs. no ventilation, (2) continuous air chute construction vs. stuffed insulation construction, and (3) opens joints in exposed kraft facing vs. taped joints. The results were compared to a concurrent study of the performance of cathedral ceilings with sloped ceiling drywall. The results show that having an air chute that ensures an air gap between the sheathing and the top of the insulation is the critical factor. Ventilation and the taping of joints were minor determinants of the moisture performance of the sheathing. These results are consistent with the results of normal cathedral ceiling construction performance.

  4. Polarization force-induced changes in the dust sheath formation

    SciTech Connect

    Mayout, Saliha; Bentabet, Karima; Tribeche, Mouloud

    2015-09-15

    The modifications arising in the dusty plasma sheath structure due to the presence of polarization forces acting on the dust grains are investigated. The corresponding appropriate Bohm criterion for sheath formation is obtained. It is found that the critical Mach number, beyond which the dusty plasma electrostatic sheath sets in, decreases whenever the polarization effects become important. In addition, when the polarization force dominates over the electrical one, the dust plasma sheath cannot set in. This happens whenever the dust grain size exceeds a critical threshold. Moreover, the sheath electrostatic potential-gradient becomes abruptly steep, and the sheath thickness becomes broader as the polarization force effects strengthen.

  5. Dural ectasia of the optic nerve sheath

    PubMed Central

    Kacem, Hanane Hadj; Hammani, Lehcen; Ajana, Ali; Nassar, Itimad

    2014-01-01

    Optic nerve dural ectasia is a rare cause of optic nerve sheath enlargement due to the accumulation of CSF around the optic nerve with no associated pathology. It diagnosed by MRI studies and can follow benign or sometimes an unfavorable course. We describe the case of a 24-day-old female referred for a visual blurring, which we diagnosed as a dural ectasia of the optic nerve sheath by MRI and confirmed in surgical intervention. We present this case report to illustrate the classic imaging features of the disease. PMID:25374645

  6. 56. POWDER MAGAZINE, VIEW OF INTACT WOOD SHEATHING ON THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    56. POWDER MAGAZINE, VIEW OF INTACT WOOD SHEATHING ON THE SOUTHWEST REAR VENTILATION PASSAGE. (SHEATHING HELP CONTROL HUMIDITY AND DECREASE DANGER OF MAETAL STRIKING STONE AND SPARKING.) - Fort Monroe, Fortress, Hampton, Hampton, VA

  7. ULTRASTRUCTURE OF THE PRAWN NERVE SHEATHS

    PubMed Central

    Doggenweiler, C. F.; Heuser, John E.

    1967-01-01

    The sheaths from freshly teased nerve fibers of the prawn exhibit a positive radial birefringence, consistent with their EM appearance as highly organized laminated structures composed of numerous thin cytoplasmic sheets or laminae bordered by unit membranes and arranged concentrically around the axon. The closely apposed membranes in these sheaths are fragile and often break down into rows of vesicles during fixation. Desmosome-like attachment zones occur in many regions of the sheath. The membranes within these zones resist vesiculation and thereby provide a "control" region for relating the type of vesicles formed in the fragile portions of the sheaths to the specific fixation conditions. It is proposed that during fixation the production of artifactual vesicles is governed by an interplay of three factors: (a) direct chemical action of the fixative on the polar strata of adjacent unit membranes, (b) osmotic forces applied to membranes during fixation, and (c) the pre-existing natural relations between adjacent membranes. It is found that permanganate best preserves the continuity of the membranes but will still produce vesicles if the fixative exerts severe osmotic forces. These results support other reports (19) of the importance of comparing tissues fixed by complementary procedures so that systematic artifacts will not be described as characteristic of the natural state. PMID:4166578

  8. Diagnosis of optic nerve sheath meningioma during optic nerve sheath decompression.

    PubMed

    Meeker, Austin R; Ko, Melissa W; Carruth, Bryant P; Strumpf, Kenneth B; Bersani, Thomas A

    2017-02-01

    Optic nerve sheath meningioma (ONSM) is typically diagnosed based on clinical suspicion and imaging characteristics and is most often treated with radiation. Historically, biopsy, optic nerve sheath decompression, and debulking surgeries have been avoided for fear of optic nerve vascular disruption and tumor spread into the orbit. This is a case of a 48-year-old man who presented with unilateral optic disc edema, declining visual acuity, and a visual field defect. Despite an initial improvement with acetazolamide, his vision subsequently worsened. With an elevated lumbar puncture opening pressure and imaging showing right optic nerve sheath enhancement, the differential diagnosis included ONSM, perineuritis and idiopathic intracranial hypertension (IIH). Optic nerve sheath decompression (ONSD) with biopsy was performed, simultaneously decompressing the nerve and yielding a sample for pathologic analysis. A pathologic diagnosis of ONSM was made and treatment with radiation was subsequently initiated, but vision began to improve after the surgical decompression alone.

  9. Radio-frequency sheath-plasma interactions with magnetic field tangency points along the sheath surface

    SciTech Connect

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2013-08-15

    Computer simulations of radio-frequency (RF) waves propagating across a two-dimensional (2D) magnetic field into a conducting boundary are described. The boundary condition for the RF fields at the metal surface leads to the formation of an RF sheath, which has previously been studied in one-dimensional models. In this 2D study, it is found that rapid variation of conditions along the sheath surface promote coupling of the incident RF branch (either fast or slow wave) to a short-scale-length sheath-plasma wave (SPW). The SPW propagates along the sheath surface in a particular direction dictated by the orientation of the magnetic field with respect to the surface, and the wave energy in the SPW accumulates near places where the background magnetic field is tangent to the surface.

  10. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  11. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  12. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  13. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  14. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  15. Sheath waves observed on OEDIPUS A

    NASA Astrophysics Data System (ADS)

    James, H. G.; Balmain, K. G.; Bantin, C. C.; Hulbert, G. W.

    1995-01-01

    An important novel feature of the tethered sounding rocket experiment OEDIPUS A (Observations of Electric-field Distributions in the Ionospheric Plasma—A Unique Strategy) was its direct excitation and detection of electromagnetic waves on conductors in space plasmas. We present quantitative evidence about sheath waves excited in the ionosphere by a high-frequency transmitter on one end of the 1-km tether and detected by a synchronized receiver on the other end. An important characteristic of sheath waves is their sequence of sharply defined passbands and stop bands in the frequency range 0.1-5 MHz. The lowest passband is between 0.1 MHz and the plasma frequency near 2 MHz, the bandwidth where existing theory predicts sheath waves. Resonance fringes in this band have been scaled to determine the phase and group refractive indices of sheath waves. These agree reasonably well with the theory, considering the approximations therein. Passbands and stop bands observed in the range between 2 and 5 MHz are not expected on the basis of the current theory. In this range, band limits have clear signatures of the interaction of the tether fields with electrostatic cyclotron waves. Finite wire moment method modeling of the payload shows that in the low-frequency passband, RF coupling along the tether is increased by 20 dB over vacuum conditions. Similarly, isolation is greater than vacuum isolation in the stop bands. Because sheath waves at frequencies up to 2 MHz are guided efficiently along conductors in plasma, they are a significant design issue in the electromagnetic compatibility of avionics at frequencies up to HF on large metal space structures.

  16. Cadaveric study of zone 2 flexor hallucis longus tendon sheath.

    PubMed

    Lui, Tun Hing; Chan, Kwok Bill; Chan, Lap Ki

    2010-06-01

    The purpose of this study was to investigate the anatomy of the zone 2 flexor hallucis longus (FHL) tendon sheath. Dissection of the zone 2 FHL tendon sheath was performed in 12 feet of 6 cadavers. The tendon sheath was subdivided into proximal fibrous (zone 2A) and distal fascial (zone 2B) parts. The lengths of the zone 2A and 2B FHL tendon were measured and represented the length of the corresponding tendon sheaths, and the relation of the medial plantar nerve to each part of the zone 2 FHL tendon sheath was studied. In all specimens there were fibrous and fascial components of the zone 2 FHL tendon sheath. The medial plantar nerve crossed the zone 2B tendon sheaths and then became plantar lateral to the sheath in 7 specimens. The distance between the medial plantar nerve and the orifice of the zone 2A tendon sheath averaged 7.6 mm. The distance between the medial plantar nerve and the junction between zones 2A and 2B averaged 3.2 mm. The distance between the medial plantar nerve and the distal end of the zone 2B tendon sheath averaged 4.2 mm. The mean length of the zone 2A tendon sheath was 35.9 mm, and the mean length of the zone 2B tendon sheath was 30.5 mm. The zone 2 FHL tendon sheath can be subdivided into a proximal fibrous zone (2A) and a distal fascial zone (2B). Because of the close proximity of the medial plantar nerve to the tendon sheath, there is a significant risk of iatrogenic nerve injury when surgical procedures are performed in zone 2B. An understanding of the anatomy of the zone 2 FHL tendon sheath is useful for the safe practice of zone 2 FHL tendoscopy. Copyright (c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

  17. Measurement of the sheath capacitance of a planar probe

    SciTech Connect

    Oh, Se-Jin; Lee, Young-Kwang; Chung, Chin-Wook

    2011-10-15

    The sheath capacitance was measured on a planar probe dc-biased with respect to the plasma potential using the phase sensitive detection method in the region separated from the rf discharge plasmas by an immersed grid. It was observed that the sheath capacitance was negative when the collecting electrode of the probe was positioned downward toward the grid and biased near the plasma potential. This indicates that a double sheath had built up near the probe electrode. This tendency can be explained by the sheath capacitance, which is calculated using Poisson's equation with a non-zero electrical field and an ion velocity condition at the sheath edge.

  18. How to Patch Active Plasma and Collisionless Sheath: Pragmatical Guide

    NASA Astrophysics Data System (ADS)

    Shneider, Mikhail N.; Kaganovich, Igor D.

    2002-11-01

    Most plasmas have very thin sheath compared with plasma dimension. This necessitates separate calculation of plasma and sheath. Bohm criterion provides boundary condition for calculation of plasma profiles. To calculate sheath properties a value of electric field at the plasma-sheath interface has to be specified in addition to Bohm criterion. The value of the boundary electric field and robust procedure to approximately patch plasma and collisionless sheath with a very good accuracy is reported. Additional information on the subject will be posted in http://www.pppl.gov/pub/report/2002/ http://arxiv.org/abs/physics/ Work supported by the Princeton Plasma Physics Laboratory through a University Research Support Program.

  19. Benchmarking sheath subgrid boundary conditions for macroscopic-scale simulations

    NASA Astrophysics Data System (ADS)

    Jenkins, T. G.; Smithe, D. N.

    2015-02-01

    The formation of sheaths near metallic or dielectric-coated wall materials in contact with a plasma is ubiquitous, often giving rise to physical phenomena (sputtering, secondary electron emission, etc) which influence plasma properties and dynamics both near and far from the material interface. In this paper, we use first-principles PIC simulations of such interfaces to formulate a subgrid sheath boundary condition which encapsulates fundamental aspects of the sheath behavior at the interface. Such a boundary condition, based on the capacitive behavior of the sheath, is shown to be useful in fluid simulations wherein sheath scale lengths are substantially smaller than scale lengths for other relevant physical processes (e.g. radiofrequency wavelengths), in that it enables kinetic processes associated with the presence of the sheath to be numerically modeled without explicit resolution of spatial and temporal sheath scales such as electron Debye length or plasma frequency.

  20. Structural characterization of highly branched glucan sheath from Ceriporiopsis subvermispora.

    PubMed

    Suzuki, Daisuke; Nishimura, Hiroshi; Yoshioka, Koichi; Kaida, Rumi; Hayashi, Takahisa; Takabe, Keiji; Watanabe, Takashi

    2017-02-01

    Wood rotting basidiomycetes produce extracellular mucilaginous sheaths interfacing fungal hyphae and plant biomass. While the versatility of these fungal sheaths has been addressed, sheaths generated by selective white-rot fungi remain poorly understood. To fill this gap, the sheath produced by the basidiomycete Ceriporiopsis subvermispora, which degrades lignin while inflicting limited cellulose damage, was analyzed in this study. Fluorescence and transmission electron microscopy revealed that the sheath formed three days after inoculation into a beech wood slice on an agar plate and was embedded at the interface between fungal hyphae and wood cell walls. The sheath's chemical structure was evaluated from fungus cultures in a liquid medium containing [U-(13)C6]-d-glucose and beech wood slices. Compositional analysis, methylation analysis, and (13)C NMR demonstrated that the sheath mainly consisted of a comb-like β-1,6-glucopyranose residue-branched β-1,3-glucan, which is advantageous to retain water and extracellular secondary metabolites.

  1. Continuum-kinetic approach to sheath simulations

    NASA Astrophysics Data System (ADS)

    Cagas, Petr; Hakim, Ammar; Srinivasan, Bhuvana

    2016-10-01

    Simulations of sheaths are performed using a novel continuum-kinetic model with collisions including ionization/recombination. A discontinuous Galerkin method is used to directly solve the Boltzmann-Poisson system to obtain a particle distribution function. Direct discretization of the distribution function has advantages of being noise-free compared to particle-in-cell methods. The distribution function, which is available at each node of the configuration space, can be readily used to calculate the collision integrals in order to get ionization and recombination operators. Analytical models are used to obtain the cross-sections as a function of energy. Results will be presented incorporating surface physics with a classical sheath in Hall thruster-relevant geometry. This work was sponsored by the Air Force Office of Scientific Research under Grant Number FA9550-15-1-0193.

  2. Optic Nerve Sheath Mechanics in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Feola, Andrew; Gleason, Rudy; Mulugeta, Lealem; Myers, Jerry; Nelson, Emily; Samuels, Brian; Ethier, C. Ross

    2015-01-01

    Visual Impairment and Intracranial Pressure (VIIP) syndrome results in a loss of visual function and occurs in astronauts following long-duration spaceflight. Understanding the mechanisms that lead to the ocular changes involved in VIIP is of critical importance for space medicine research. Although the exact mechanisms of VIIP are not yet known, it is hypothesized that microgravity-induced increases in intracranial pressures (ICP) drive the remodeling of the optic nerve sheath, leading to compression of the optic nerve which in turn may reduce visual acuity. Some astronauts present with a kink in the optic nerve after return to earth, suggesting that tissue remodeling in response to ICP increases may be taking place. The goal of this work is to characterize the mechanical properties of the optic nerve sheath (dura mater) to better understand its biomechanical response to increased ICP.

  3. Endoscopic Synovectomy of Peroneal Tendon Sheath.

    PubMed

    Lui, Tun Hing

    2017-06-01

    Peroneal tenosynovitis usually responds to conservative therapy. Early diagnosis and management are imperative because improper or delayed diagnosis and treatment of peroneal tenosynovitis may lead to progression of the tenosynovitis to peroneal tendon rupture, ultimately limiting the benefit of nonoperative treatment. For refractory cases, endoscopic tenosynovectomy is indicated. The purpose of this Technical Note is to report a minimally invasive approach to perform a synovectomy of zones 1 and 2 of the peroneal tendon sheath.

  4. Experimental Investigations of the Lunar Photoelectron Sheath

    NASA Astrophysics Data System (ADS)

    Dove, A.; Sternovsky, Z.; Wang, X.; Robertson, S. H.; Lapanse, C.; Horanyi, M.; Collette, A.

    2010-12-01

    Solar ultraviolet radiation incident upon the dayside lunar surface produces a photoelectron gas that dominates the near-surface plasma environment, with a typical density of 60 cm-3 and a characteristic scale-length of ~1 m. It has traditionally been difficult to produce a photoelectron gas with sufficient density in a laboratory settings to study its properties. In our initial experiments, the characterization of the photoelectron density above a Zr surface (work function W=4.4 eV) illuminated by Xe excimer lamps (peak emission at a wavelength of 172 nm) indicated that a sheath with a Debye length on the order of 10 cm formed. We characterize the photoelectron population above the surface by utilizing an emissive probe to map the electric potential distribution above the surface, and a Langmuir probe to determine the number density and temperature of the photoelectrons. A grid is placed 7.5 cm above the Zr surface to repel photoelectrons emitted from the chamber walls. Emissive probe measurements show a potential dip of about 2 V extending ~1 cm above the zirconium surface. The size of this potential well is dependent on the number of lamps illuminating the surface, as the density of photoelectrons above the surface increases with greater illumination. The electrons in the sheath have a Maxwellian distribution with an electron temperature around 1 eV (maximum energies are expected to be approximately 2.8 eV). We will use this experimental apparatus to characterize the photoelectron sheath above other surfaces; powders, such as CeO2 have similar work functions, but different photoelectric yields. Lunar soil simulants are expected to have approximately an order of magnitude smaller yield than metallic surfaces, which will act to increase the characteristic length of the photoelectron sheath above the surface. The experiments and accompanying computer simulations are used to guide the development of new instrument concepts for future in situ plasma measurements on

  5. Two Types of Magnetohydrodynamic Sheath Jets

    NASA Astrophysics Data System (ADS)

    Kaburaki, Osamu

    2009-06-01

    Recent observations of astrophysical jets emanating from various galactic nuclei strongly suggest that a double-layered structure, or a spine-sheath structure, is likely to be their common feature. We propose that such a sheath jet structure can be formed magnetohydrodynamically within a valley of the magnetic pressures, which is formed between the peaks due to the poloidal and toroidal components, with the centrifugal force acting on the rotating sheath plasma being balanced by the hoop stress of the toroidal field. The poloidal field concentrated near the polar axis is maintained by a converging plasma flow toward the jet region, and the toroidal field is developed outside the jet cone owing to the poloidal current circulating through the jet. Under such situations, the set of magnetohydrodynamic (MHD) equations allows two main types of solutions, at least, in the region far from the footpoint. The first type solution describes the jets of marginally bound nature. This type is realized when the jet temperature decreases like a virial one, and neither the pressure-gradient nor the MHD forces, which are both determined consistently, cannot completely overcome the gravity, even at infinity. The second type is realized under an isothermal situation, and the gravity is cancelled exactly by the pressure-gradient force. Hence, the jets of this type are accelerated purely by the MHD force. It is also suggested that these two types correspond, respectively, to the jets from type I and II radio galaxies in the Fanaroff-Riley classification.

  6. Experimental Observation of Sheath-presheath Instabilities

    NASA Astrophysics Data System (ADS)

    Kella, Vara Prasad; Ghosh, Joydeep; Sharma, Devendra; Chattopadhyay, Prabal K.

    2016-10-01

    Instabilities in the Sheath-presheath regime are most important phenomena that can affect the plasma-wall interaction. These instabilities can modify the particle flow velocities and distribution functions in that regime. In this present work, instabilities exists in the sheath-presheath in a low temperature plasma are observed. Experiments are carried in single ion species argon plasma and multi ion species Ar-He plasma. Experiments are carried in a stainless steel chamber with filament discharge plasma. Sheath is produced around a stainless steel grid at center of the chamber. Fluctuations from the grid and cylindrical Langmuir probe are recorded. Langmuir probe is used to get the floating potential fluctuations from presheath and bulk plasma as well. In single ion species argon plasma, there are two instabilities observed namely ion-ion counter streaming instability through mesh grid and ion acoustic instability respectively arises in the presheath. In case of multi-ion Ar-He plasma, two stream instability also explored. The neutral pressure threshold for the sustain of these instabilities also observed.

  7. Radio frequency sheaths in an oblique magnetic field

    SciTech Connect

    Myra, J. R.; D'Ippolito, D. A.

    2015-06-15

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describes the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle θ, assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath, and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general, the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.

  8. Electron Sheaths and Non-ambipolar Diffusion in Laboratory Plasma

    NASA Astrophysics Data System (ADS)

    Baalrud, Scott; Hershkowitz, Noah

    2006-10-01

    Electron sheaths were first predicted by Langmuir in 1929 when he stated that, ``with a large area, A, an anode sheath is a positive ion sheath, but that as A decreases, a point is reached where the positive ion sheath disappears and it is replaced by an electron sheath.''. We show that electron sheath formation near a positive anode depends on the anode area, Aa, as well as the area available for ion loss, Ai. When Aa/Ai< (me/mi)^1/2, the electron sheath potential monotonically decreases from the anode to the bulk plasma. When the anode is larger than this, a potential dip forms in the electron sheath to reduce the electron current lost to the anode. This potential dip is necessary to preserve global current balance and when it is present, total non-ambipolar diffusion can occur where all electrons are lost from the plasma through an electron sheath and all positive ions are lost elsewhere. Additional measurements were carried out to identify the transition from positive (ion) to negative (electron) sheaths. Data were taken in low-pressure argon plasma generated by hot filaments and confined in a multidipole chamber. I. Langmuir, Physical Review. 33, 954 (1929).

  9. Radio frequency sheaths in an oblique magnetic field

    SciTech Connect

    Myra, James R.; D'Ippolito, Daniel A.

    2015-06-01

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, θ assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.

  10. Radio frequency sheaths in an oblique magnetic field

    DOE PAGES

    Myra, James R.; D'Ippolito, Daniel A.

    2015-06-01

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, θ assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numericallymore » to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.« less

  11. Optic Nerve Sheath Mechanics in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Forte, Taylor E.; Wang, Roy; Feola, Andrew; Samuels, Brian; Myers, Jerry; Nelson, Emily; Gleason, Rudy; Ethier, C. Ross

    2016-01-01

    Visual Impairment Intracranial Pressure (VIIP) syndrome is a major concern in current space medicine research. While the exact pathology of VIIP is not yet known, it is hypothesized that the microgravity-induced cephalad fluid shift increases intracranial pressure (ICP) and drives remodeling of the optic nerve sheath. To investigate this possibility, we are culturing optic nerve sheath dura mater samples under different pressures and investigating changes in tissue composition. To interpret results from this work, it is essential to first understand the biomechanical response of the optic nerve sheath dura mater to loading. Here, we investigated the effects of mechanical loading on the porcine optic nerve sheath.Porcine optic nerves (number: 6) were obtained immediately after death from a local abattoir. The optic nerve sheath (dura mater) was isolated from the optic nerve proper, leaving a hollow cylinder of connective tissue that was used for biomechanical characterization. We developed a custom mechanical testing system that allowed for unconfined lengthening, twisting, and circumferential distension of the dura mater during inflation and under fixed axial loading. To determine the effects of variations in ICP, the sample was inflated (0-60 millimeters Hg) and circumferential distension was simultaneously recorded. These tests were performed under variable axial loads (0.6 grams - 5.6 grams at increments of 1 gram) by attaching different weights to one end of the dura mater. Results and Conclusions: The samples demonstrated nonlinear behavior, similar to other soft connective tissue (Figure 1). Large increases in diameter were observed at lower transmural pressures (approximately 0 to 5 millimeters Hg), whereas only small diameter changes were observed at higher pressures. Particularly interesting was the existence of a cross-over point at a pressure of approximately 11 millimeters Hg. At this pressure, the same diameter is obtained for all axial loads applied

  12. Simulation study of the magnetized sheath of a dusty plasma

    SciTech Connect

    Foroutan, G.; Mehdipour, H.; Zahed, H.

    2009-10-15

    Numerical solutions of stationary multifluid equations are used to study the formation and properties of the magnetized sheath near the boundary of a dusty plasma. The impacts of the strength of the magnetic field, the dust and plasma number densities, and the electron temperature on the sheath structure and spatial distributions of various quantities are investigated. It is shown that for a given angle of incidence of the magnetic field, there is a threshold magnetic field intensity above which some kind of large regular inhomogeneities develop on the spatial profile of the dust particles. The sheath thickness, the electron and ion number densities, and the absolute dust charge are strongly affected by the variation in the dust number density. The sheath demonstrates a nonlinear dependence on the electron temperature; as the electron temperature rises, the sheath first is broadened and the absolute wall potential decreases but then at higher temperatures the sheath becomes narrower and the absolute wall potential increases.

  13. Sheath insulator final test report, TFE Verification Program

    SciTech Connect

    Not Available

    1994-07-01

    The sheath insulator in a thermionic cell has two functions. First, the sheath insulator must electrically isolate the collector form the outer containment sheath tube that is in contact with the reactor liquid metal coolant. Second, The sheath insulator must provide for high uniform thermal conductance between the collector and the reactor coolant to remove away waste heat. The goals of the sheath insulator test program were to demonstrate that suitable ceramic materials and fabrication processes were available, and to validate the performance of the sheath insulator for TFE-VP requirements. This report discusses the objectives of the test program, fabrication development, ex-reactor test program, in-reactor test program, and the insulator seal specifications.

  14. Simulations of plasma sheaths using continuum kinetic models

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bhuvana; Hakim, Ammar

    2015-11-01

    Understanding plasma sheath physics is important for the performance of devices such as Hall thrusters due to the effect of energetic particles on electrode erosion. Plasma sheath physics is studied using kinetic and multi-fluid models with relevance to secondary electron emissions and plasma-surface interactions. Continuum kinetic models are developed to directly solve the Vlasov-Poisson equation using the discontinuous Galerkin method for each of the ion and electron species. A steady-state sheath is simulated by including a simple model for a neutral fluid. Multi-fluid simulations for the plasma sheath are also performed using the discontinuous Galerkin method to solve a complete set of fluid equations for each of the ion and electron species. The kinetic plasma sheath is compared to a multi-fluid plasma sheath. Supported by Air Force Office of Scientific Research.

  15. Nerve Sheath Myxoma: Report of A Rare Case

    PubMed Central

    Bhat, Amoolya; C, Vijaya; VK, Sundeep

    2015-01-01

    Nerve sheath myxoma defined by Harkin and Reed is an uncommon benign neoplasm with nerve sheath like features. It has several cytological and histological differential diagnoses. One such lesion is neurothekeoma, which can be differentiated using immunohistochemistry. In most of the previous reports nerve sheath myxoma and neurothekeoma were considered synonymous and were often confused for one another. This case report separates the two using immunohistochemistry. Also, the cytological features of nerve sheath myxoma are not well documented in the past. This case report attempts to display the cyto-morphology of nerve sheath myxoma. We report a rare case of nerve sheath myxoma diagnosed on cytological features confirmed by histopathology and immunohistochemistry in a 32-year-old lady who presented with an asymptomatic nodule over the left cervical area and discuss its cyto-histological mimics. PMID:26023558

  16. Nerve sheath myxoma: report of a rare case.

    PubMed

    Bhat, Amoolya; Narasimha, Apaparna; C, Vijaya; Vk, Sundeep

    2015-04-01

    Nerve sheath myxoma defined by Harkin and Reed is an uncommon benign neoplasm with nerve sheath like features. It has several cytological and histological differential diagnoses. One such lesion is neurothekeoma, which can be differentiated using immunohistochemistry. In most of the previous reports nerve sheath myxoma and neurothekeoma were considered synonymous and were often confused for one another. This case report separates the two using immunohistochemistry. Also, the cytological features of nerve sheath myxoma are not well documented in the past. This case report attempts to display the cyto-morphology of nerve sheath myxoma. We report a rare case of nerve sheath myxoma diagnosed on cytological features confirmed by histopathology and immunohistochemistry in a 32-year-old lady who presented with an asymptomatic nodule over the left cervical area and discuss its cyto-histological mimics.

  17. Steerable sheath technology in the ablation of atrial fibrillation.

    PubMed

    Joseph, Jubin; Wong, Kelvin C K; Ginks, Matthew R; Bashir, Yaver; Betts, Timothy R; Rajappan, Kim

    2013-12-01

    Steerable sheaths have been shown to reduce procedure time in the catheter ablation of atrial fibrillation (AF), where catheter positioning and stability is typically challenging. This review critically addresses and highlights the recent developments in design of sheaths used to manipulate the ablation catheter and how these developments may impact on the ablation procedure itself, in particular the likelihood of first-time success. Patents relating to steerable sheaths are reviewed and discussed to gauge potential future developments in this area.

  18. Nondestructive testing of metallic sheath for internally cooled superconductor

    SciTech Connect

    McClung, R.W.; Cook, K.V.; Dodd, C.V.; Smith, J.H.

    1983-01-01

    For quality assurance in the Oak Ridge National Laboratory Large Coil Program, we developed ultrasonic and eddy-current techniques to examine the JBK-75 alloy sheath for superconducting cable for a large magnet. Ultrasound was used to examine the strip before forming into the sheath, and eddy currents were used to examine the seam weld after the sheath had been formed around the cable.

  19. Kinetic model for the collisionless sheath of a collisional plasma

    SciTech Connect

    Tang, Xian-Zhu Guo, Zehua

    2016-08-15

    Collisional plasmas typically have mean-free-path still much greater than the Debye length, so the sheath is mostly collisionless. Once the plasma density, temperature, and flow are specified at the sheath entrance, the profile variation of electron and ion density, temperature, flow speed, and conductive heat fluxes inside the sheath is set by collisionless dynamics, and can be predicted by an analytical kinetic model distribution. These predictions are contrasted here with direct kinetic simulations, showing good agreement.

  20. A model for tailored-waveform radiofrequency sheaths

    NASA Astrophysics Data System (ADS)

    Chabert, P.; Turner, M. M.

    2017-06-01

    The sheath physics of radiofrequency plasmas excited by a sinusoidal waveform is reasonably well understood, but the existing models are complicated and are not easily extended to the more complex waveforms recently introduced in applications. Turner and Chabert (2014 Appl. Phys. Lett. 104 164102) proposed a model for collisionless sheaths that can easily be solved for arbitrary waveforms. In this paper we extend this model to the case of collisional sheaths in the intermediate pressure regime. Analytical expressions are derived for the electric field, the electric potential and the density profiles in the sheath region. The collisionless and collisional models are compared for a pulsed-voltage waveform.

  1. Electrical characterization of a capacitive rf plasma sheath

    NASA Astrophysics Data System (ADS)

    Gahan, D.; Hopkins, M. B.

    2007-01-01

    The authors report on an experimental system designed to investigate and characterize capacitive radio frequency (rf) sheaths. An electrode mounted in an inductive plasma reactor and driven with separate rf and direct current (dc) power sources is used. The advantage of this design is that the electrode sheath is decoupled from the plasma parameters. This allows detailed investigation of the sheath with different bias conditions without perturbing the bulk plasma parameters. Power coupled to ions and electrons through the sheath, at low pressure, is investigated and a method to determine the electron conduction current to the electrode, using the external dc bias, is presented.

  2. Isolation and chemical composition of the sheath of Sphaerotilus natans.

    PubMed

    Takeda, M; Nakano, F; Nagase, T; Iohara, K; Koizumi, J

    1998-06-01

    A sheathed bacterium, Sphaerotilus natans, was cultured with vigorous shaking in a medium containing peptone. Then the biomass was harvested and treated with lysozyme, sodium dodecyl sulfate, and protease. With treatment, 1.6 mg of sheaths was obtained from 15 mg of biomass. For the preparation of sheaths of high purity, cultivation must be in the absence of glucose with sufficient aeration to prevent poly(3-hydroxybutyrate) accumulation. Carbohydrate (54.1%), protein (12.2%), and lipid (1-3%) were detected in the sheaths by colorimetric reactions and solvent extraction. Gas-liquid chromatography showed glucose and galactosamine to be present in the molar ratio of 1:4. The most abundant amino acids in the sheath protein were glycine (49.2 mol%) and cysteine (24.6 mol%). The sheaths were resistant to agents that reduce disulfide bonds (dithiothreitol and 2-mercaptoethanol) and to protease. However, sheathes were degraded completely by hydrazine, and a heteropolysaccharide composed of glucose and galactosamine (1:4) was released. The weight-average molecular weight of the polysaccharide was estimated to be 1.2 x 10(5) by gel filtration chromatography with a low-angle laser-light scattering photometer and a rotation index detector. A ladder of 1.5-kDa peptides separable by sodium dodecyl sulfate gel electrophoresis was obtained by partial hydrolysis of sheaths, suggesting the sheath protein has repeating units of 1.5 kDa.

  3. Sheath effects on DEMETER ion drift measurements

    NASA Astrophysics Data System (ADS)

    Marchand, Richard; Knutson, Nelson; Berthelier, Jean-Jacques

    2010-08-01

    The "Instrument d'Analyse du Plasma" on DEMETER includes an ion drift meter used to measure the direction of the incoming ram plasma ( Berthelier et al., 2006a, b ). Given the velocity of the satellite, and expected flow velocities of plasma along DEMETER's orbit, it is estimated that at mid latitudes, the direction of incident plasma as measured by IAP should be within approximately 2° of the ram direction. Yet, significantly larger angular deviations are measured routinely. An important assumption made in the interpretation of onboard instruments, such as IAP, is that neither the spacecraft nor the instrument significantly perturb the plasma that is being measured. In view of the large observed angular deviations, this paper examines the possible effect of the electrostatic sheath surrounding IAP. This is done with the 3D PIC simulation code PTetra. The model uses a full 3D particle in cell code with unstructured tetrahedral mesh capable of accurately representing the satellite geometry. The mesh is also adaptive so as to provide a fine spatial resolution in the vicinity of the particle sensor where it is needed, and a coarse resolution in regions where plasma parameters vary over a longer scale length. Calculation results show that while particle deflection associated with the electrostatic sheath near IAP can account for appreciable angular deflections for representative ionospheric plasmas, they are typically smaller than the ones observed. Additionally, the model is unable to reproduce the latitudinal dependence of the observed large deflection angles. It is concluded that sheath effects may cause appreciable distortions on the IAP type of ion flow meter instruments, and on other particle sensors in general. The larger observed deviations and their latitudinal dependence, however, must be attributable to other physical processes not accounted for in the model.

  4. Lunar photoelectron sheath and levitation of dust

    NASA Astrophysics Data System (ADS)

    Sodha, M. S.; Mishra, S. K.

    2014-09-01

    The decision to launch Luna Glob and Luna Resus satellites, carrying instrumentation to investigate the structure of photoelectron sheath and levitation of dust particles in the sheath, adjacent to the surface of the moon has intensified interest in this exciting area. The present analysis incorporates the following novel features: (i) In contrast to intuitive half Maxwellian (M) distribution of velocities of the photoelectrons, emitted from the surface of the moon, which corresponds to an arbitrary temperature, a well-established half Fermi Dirac (F-D) distribution [R. H. Fowler, Phys. Rev. 38, 45 (1931)] has been used, (ii) the profiles for electric potential, electric field, and electron density have been derived (not a priori assumed), (iii) an expression for the rate of electron accretion on a positively charged dust particle, which takes account of the anisotropic flux of electrons has been derived and used in the analysis, and (iv) a derived (rather than intuitive) expression for the rate of photoelectron emission from a positively charged dust particle has been used for the first time in such analyses. The profiles of the electric potential, electric field, and electron density in the photoelectric sheath have been evaluated for typical lunar environment and used to obtain the profile of the radius of a dust particle for levitation. The dependence of the electric potential on the surface of the moon on the parameters of the solar wind and photo-efficiency of the material of moon's surface has also been discussed. It is seen that the results based on half F-D distribution are significantly different from those obtained on the basis of M-distribution.

  5. Advances in target normal sheath acceleration theory

    SciTech Connect

    Passoni, M.; Sgattoni, A.; Perego, C.; Batani, D.

    2013-06-15

    A theoretical model of the Target Normal Sheath Acceleration (TNSA) process, able to go beyond the limits of available descriptions, is developed. It allows to achieve a more satisfactory interpretation of TNSA. The theory, also supported by two dimensional particle-in-cell simulations, elucidates the role played by the main laser and target parameters. Comparison between model predictions and experimental data related to the target thickness dependence of the maximum ion energy is discussed, showing satisfactory agreement. The model can be used as a simple but effective tool to guide the design of future experiments.

  6. Controversies in ureteroscopy: Wire, basket, and sheath

    PubMed Central

    Rizkala, Emad R; Monga, Manoj

    2013-01-01

    In the last one to two decades, flexible ureteroscopy has rapidly expanded its role in the treatment of urologic stone disease. With the frequent and expanded use of flexible ureteroscopy, other ancillary instruments were developed in order to ease and facilitate this technique, such as ureteral access sheaths (UAS) and a variety of wires and baskets. These developments, along with improved surgeon ureteroscopic competence, have often brought into question the need to implement the “traditional technique” of flexible ureteroscopy. In this review, we discuss a brief history of flexible ureteroscopy, its expanded indications, and the controversy surrounding the use of UAS, wires, and baskets. PMID:24082447

  7. Rarefaction solitons initiated by sheath instability

    SciTech Connect

    Levko, Dmitry

    2015-09-15

    The instability of the cathode sheath initiated by the cold energetic electron beam is studied by the one-dimensional fluid model. Numerical simulations show the generation of travelling rarefaction solitons at the cathode. It is obtained that the parameters of these solitons strongly depend on the parameters of electron beam. The “stretched” variables are derived using the small-amplitude analysis. These variables are used in order to obtain the Korteweg-de Vries equation describing the propagation of the rarefaction solitons through the plasma with cold energetic electron beam.

  8. Target normal sheath acceleration sheath fields for arbitrary electron energy distribution

    SciTech Connect

    Schmitz, Holger

    2012-08-15

    Relativistic electrons, generated by ultraintense laser pulses, travel through the target and form a space charge sheath at the rear surface which can be used to accelerate ions to high energies. If the laser pulse duration is comparable or shorter than the time needed for the electrons to travel through the target, the electrons will not have the chance to form an equilibrium distribution but must be described by a non-equilibrium distribution. We present a kinetic theory of the rear sheath for arbitrary electron distribution function f(E), where E is the electron energy, and evaluate it for different shapes of f(E). We find that the far field is mainly determined by the high energy tail of the distribution, a steep decay of f(E) for high energies results in a small electric field and vice versa. The model is extended to account for electrons escaping the sheath region thereby allowing a finite potential drop over the sheath. The consequences of the model for the acceleration of ions are discussed.

  9. Anode sheath contributions in plasma thrusters

    NASA Astrophysics Data System (ADS)

    Biblarz, Oscar; Riggs, John F.

    1993-06-01

    Contributions of the anode to MPD plasma thruster performance are considered. High energy losses at the electrode, surface erosion, and sheath/ionization effects must be controlled in designs of practical interest. Current constriction or spotting at the electrode, resulting in localized surface damage and considerable throat erosion, is shown to be related to the rise in T(e) above the gas temperature T(0). An elementary 1D description of a collisional sheath which highlights the role of T(e) is presented. For a large temperature nonequilibrium the 1D approach fails to give reasonable answers and a multidimensional description is necessary. Thus, current constriction at the electrode surface may be precipitated by the elevation of T(e). Thermionic arc breakdown is proposed as an explanation for the observed breakdown voltages below the ionization potentials. A review of transpiration cooling as a means of recouping anode power is included. Active anode cooling via transpiration cooling would result in (1) quenching T(e), (2) adding 'hot' propellant to exhaust, and (3) reducing the local electron Hall parameter. However, significant technical problems remain.

  10. Electrohydrodynamic direct-writing orderly pattern with sheath gas focusing

    NASA Astrophysics Data System (ADS)

    Zheng, Jianyi; Zhang, Kai; Jiang, Jiaxin; He, Guangqi; Xu, Lei; Liu, Yifang; Liu, Juan; Wu, Dezhi; Zheng, Gaofeng

    2016-11-01

    Laminar sheath gas is introduced to increase the stability of Electrohydrodynamic Direct-Writing (EDW). The external stretching force from sheath gas promotes the ejection threshold, the diameter of jet and printed fibers as well. The critical voltage decreases with the increase of sheath gas pressure. The stretching force from sheath gas decreases the diameter of printed fiber as well as that of charged jet. As sheath gas pressure increases from 0 to 25 kPa, the average diameter of micro/nano structure reduces from 4.46 μ m to 845.25 nm. The laminar field flow of sheath gas shelters the charged jet free from the surrounding interferences, and helps charged jet to move in a straight line. With the help of sheath gas, the stability of charged jet can be improved to direct-write precise complex micro-pattern. The position precision of direct-written pattern is less than 5 μ m . As a novel method, EDW with laminar sheath gas would promote the deposition precision of printed micro/nano structure and its application.

  11. Dynamic reversibility of hydrodynamic focusing for recycling sheath fluid.

    PubMed

    Hashemi, Nastaran; Howell, Peter B; Erickson, Jeffrey S; Golden, Joel P; Ligler, Frances S

    2010-08-07

    The phenomenon of "unmixing" has been demonstrated in microfluidic mixers, but here we manipulate laminar flow streams back to their original positions in order to extend the operational utility of an analytical device where no mixing is desired. Using grooves in the channel wall, we passively focus a sample stream with two sheath streams to center it in a microchannel for optical analysis. Even though the sample stream is completely surrounded by sheath fluid, reversing the orientation of the grooves in the channel walls returns the sample stream to its original position with respect to the sheath streams. We demonstrate the separation of the sample stream from the contiguous sheath streams and the recycling of the sheath fluid using the reversibility of laminar flow. Polystyrene microspheres and fluorescent dye were used to quantify the performance of the unsheathing process. We found that the maximum numbers of microspheres and all of the fluorescent dye were recaptured at sheath recycling levels <92%. The use of this sheathing technique has previously been demonstrated in a sensitive microflow cytometer; the unsheathing capability now provides the opportunity to recover particles from the sensor with minimal dilution or to recycle the sheath fluid for long-term unattended operation.

  12. Electrospinning jet behaviors under the constraints of a sheath gas

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Jiang, Jiaxin; Li, Wenwang; Wang, Xiang; Zhang, Kai; Zhu, Ping; Zheng, Gaofeng

    2016-11-01

    Increasing the ejection efficiency and uniformity of nanofibers is the key to applications of electrospinning technology. In this work, a novel electrospinning spinneret with a sheath gas passageway is designed. The frictional resistance that stems from the sheath gas provides additional stretching and restriction forces on the jet. The sheath gas also reduces interference and enhances the stability of the charged jet. A bead-on-strain simulation model is built up to determine the constraint effects of the sheath gas. Simulation results show that the sheath gas decreases the motion area and increases the stretching ratio of the liquid jet. The stretching force from the sheath gas decreases the diameter and increases the uniformity of the nanofiber. As the gas pressure increases from 0 kPa to 50 kPa, the critical voltage of the jet ejection decreases from 8.4 kV to 2.5 kV, the diameter of the nanofiber deposition zone decreases from 40 cm to 10 cm, and the diameter of the nanofibers decreases from 557.97 nm to 277.73 nm. The uniformity of nanofibers can be improved significantly using a sheath gas. The sheath gas contributes to the rapid deposition of a uniform nanofibrous membrane and the industrial applications of electrospinning.

  13. Anode Sheath Switching in a Carbon Nanotube Arc Plasma

    SciTech Connect

    Abe Fetterman, Yevgeny Raitses, and Michael Keidar

    2008-04-08

    The anode ablation rate is investigated as a function of anode diameter for a carbon nanotube arc plasma. It is found that anomalously high ablation occurs for small anode diameters. This result is explained by the formation of a positive anode sheath. The increased ablation rate due to this positive anode sheath could imply greater production rate for carbon nanotubes.

  14. Two simple and rugged designs for creating microfluidic sheath flow

    PubMed Central

    Howell, Peter B.; Golden, Joel P.; Hilliard, Lisa R.; Erickson, Jeffrey S.; Mott, David R.; Ligler, Frances S.

    2009-01-01

    A simple design capable of 2-dimensional hydrodynamic focusing is proposed and successfully demonstrated. In the past, most microfluidic sheath flow systems have often only confined the sample solution on the sides, leaving the top and bottom of the sample stream in contact with the floor and ceiling of the channel. While relatively simple to build, these designs increase the risk of adsorption of sample components to the top and bottom of the channel. A few designs have been successful in completely sheathing the sample stream, but these typically require multiple sheath inputs and several alignment steps. In the designs presented here, full sheathing is accomplished using as few as one sheath input, which eliminates the need to carefully balance the flow of two or more sheath inlets. The design is easily manufactured using current microfabrication techniques. Furthermore, the sample and sheath fluid can be subsequently separated for recapture of the sample fluid or re-use of the sheath fluid. Designs were demonstrated in poly(dimethylsiloxane) (PDMS) using soft lithography and poly(methyl methacrylate) (PMMA) using micromilling and laser ablation. PMID:18584084

  15. A generalized BC for radio-frequency sheaths

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.

    2015-12-01

    A new radio-frequency (rf) sheath boundary condition (BC) is described and applied to the problem of far field sheaths. The new BC generalizes the one presently used in rf codes to include: (1) an arbitrary magnetic field angle, (2) the full complex impedance, (3) mobile ions, (4) unmagnetized ions, and (5) the magnetic pre-sheath. For a given wave-propagation (macro) problem, root-finding is used to match the impedance of the rf wave with that of the micro-sheath problem. For a model far-field sheath problem, it is shown that the structure of the (multiple) roots with the new BC is similar to that with the capacitive BC, but the location of the resonance changes when the full impedance is used.

  16. Gas insulated transmission line having low inductance intercalated sheath

    DOEpatents

    Cookson, Alan H.

    1978-01-01

    A gas insulated transmission line including an outer sheath, an inner conductor disposed within the outer sheath, and an insulating gas between the inner conductor and the outer sheath. The outer sheath comprises an insulating tube having first and second ends, and having interior and exterior surfaces. A first electrically conducting foil is secured to the interior surface of the insulating tube, is spirally wound from one tube end to the second tube end, and has a plurality of overlapping turns. A second electrically conducting foil is secured to the exterior surface of the insulating tube, and is spirally wound in the opposite direction from the first electrically conducting foil. By winding the foils in opposite directions, the inductances within the intercalated sheath will cancel each other out.

  17. What is the size of a floating sheath? An answer

    NASA Astrophysics Data System (ADS)

    Voigt, Farina; Naggary, Schabnam; Brinkmann, Ralf Peter

    2016-09-01

    The formation of a non-neutral boundary sheath in front of material surfaces is universal plasma phenomenon. Despite several decades of research, however, not all related issues are fully clarified. In a recent paper, Chabert pointed out that this lack of clarity applies even to the seemingly innocuous question ``What the size of a floating sheath?'' This contribution attempts to provide an answer that is not arbitrary: The size of a floating sheath is defined as the plate separation of an equivalent parallel plate capacitor. The consequences of the definition are explored with the help of a self-consistent sheath model, and a comparison is made with other sheath size definitions. Deutsche Forschungsgemeinschaft within SFB TR 87.

  18. A Coupled Plasma-Sheath Model for High Density Sources

    NASA Technical Reports Server (NTRS)

    Bose, Deepak; Govindan, T. R.; Meyyappan, M.

    2000-01-01

    High density, low pressure plasmas are used for etching and deposition in microelectronics fabrication processes. The process characteristics are strongly determined by the ion energy distribution (IED) and the ion flux arriving at the substrate that are responsible for desorption of etch products and neutral dissociation at the surface. The ion flux and energy are determined by a self- consistent modeling of the bulk plasma, where the ions and the neutral radicals are produced, and the sheath, where the ions are accelerated. Due to their widely different time scales, it is a formidable task to self-consistently resolve non-collisional sheath in a high density bulk plasma model. In this work, we first describe a coupled plasma-sheath model that attempts to resolve the non-collisional sheath in a reactor scale model. Second, we propose a semianalytical radio frequency (RF) sheath model to improve ion dynamics.

  19. Effect of collisions on photoelectron sheath in a gas

    NASA Astrophysics Data System (ADS)

    Sodha, Mahendra Singh; Mishra, S. K.

    2016-02-01

    This paper presents a study of the effect of the collision of electrons with atoms/molecules on the structure of a photoelectron sheath. Considering the half Fermi-Dirac distribution of photo-emitted electrons, an expression for the electron density in the sheath has been derived in terms of the electric potential and the structure of the sheath has been investigated by incorporating Poisson's equation in the analysis. The method of successive approximations has been used to solve Poisson's equation with the solution for the electric potential in the case of vacuum, obtained earlier [Sodha and Mishra, Phys. Plasmas 21, 093704 (2014)], being used as the zeroth order solution for the present analysis. The inclusion of collisions influences the photoelectron sheath structure significantly; a reduction in the sheath width with increasing collisions is obtained.

  20. How to Patch Active Plasma and Collisionless Sheath: Pragmatical Guide

    NASA Astrophysics Data System (ADS)

    Kaganovich, Igor D.

    2002-10-01

    Most plasmas have very thin sheath compared with plasma dimension. This necessitates separate calculation of plasma and sheath. Bohm criterion provides boundary condition for calculation of plasma profiles. To calculate sheath properties a value of electric field at the plasma-sheath interface has to be specified in addition to Bohm criterion. The value of the boundary electric field and robust procedure to approximately patch plasma and collisionless sheath with a very good accuracy is reported. Additional information on the subject is posted on the web http://www.pppl.gov/pub/report/2002/ http://arxiv.org/abs/physics/0208041. Work supported by the Department of Energy via the University Research Support Program of Princeton Plasma Physics Laboratory.

  1. An Everting Ureteral Access Sheath: Concepts and In Vitro Testing

    NASA Astrophysics Data System (ADS)

    Lee, Keith L.; Stoller, Marshall L.

    2007-04-01

    Ureteral access sheaths have been a recent innovation in facilitating ureteral stone surgery. Once properly placed, access sheaths allow the movement of ureteroscopes and other instruments through the ureter with minimal injury to the urothelium. However, there are shortcomings of the current device designs. Initial sheath placement requires significant force, and shear stress can injure the ureter. In addition, inadvertent advancement of the outer sheath without the inner introducer stylet can tear and avulse the ureter. A novel eversion design incorporating a lubricous film provides marked improvement over current access sheaths. In bench top and animal models, the eversion shealths require less force during advancement, cause less injury to the urothelial tissue, and have a lower potential of introducing extraneous materials (e.g., microbes) into a simulated urinary tract. While, the everting design provides important advantages over traditional non-everting designs, further preclinical and clinical trials are required.

  2. Similarities and distinctions of CIR and Sheath

    NASA Astrophysics Data System (ADS)

    Yermolaev, Yuri; Lodkina, Irina; Nikolaeva, Nadezhda; Yermolaev, Michael

    2016-04-01

    On the basis of OMNI data and our catalog of large scale solar wind (SW) streams during 1976-2000 [Yermolaev et al., 2009] we study the average temporal profiles for two types of compressed regions: CIR (corotating interaction region - compressed region before High Speed Stream (HSS)) and Sheath (compressed region before fast Interplanetary CMEs (ICMEs), including Magnetic Cloud (MC) and Ejecta). As have been shown by Nikolaeva et al, [2015], the efficiency of magnetic storm generation is ~50% higher for Sheath and CIR than for ICME (MC and Ejecta), i.e. reaction magnetosphere depends on type of driver. To take into account the different durations of SW types, we use the double superposed epoch analysis (DSEA) method: rescaling the duration of the interval for all types in such a manner that, respectively, beginning and end for all intervals of selected type coincide [Yermolaev et al., 2010; 2015]. Obtained data allows us to suggest that the formation of all types of compression regions has the same physical mechanism irrespective of piston (HSS or ICME) type and differences are connected with geometry and full jumps of speed in edges of compression regions. If making the natural assumption that the gradient of speed is directed approximately on normal to the piston, CIR has the largest angle between the gradient of speed and the direction of average SW speed, and ICME - the smallest angle. The work was supported by the Russian Foundation for Basic Research, projects 13-02-00158, 16-02-00125 and by Program of Presidium of the Russian Academy of Sciences. References: Nikolaeva, N. S. , Yu. I. Yermolaev, and I. G. Lodkina (2015), Modeling of the Corrected Dst* Index Temporal Profile on the Main Phase of the Magnetic Storms Generated by Different Types of Solar Wind, Cosmic Research, Vol. 53, No. 2, pp. 119-127. Yermolaev, Yu. I., N. S. Nikolaeva, I. G. Lodkina, and M. Yu. Yermolaev (2009), Catalog of Large-Scale Solar Wind Phenomena during 1976-2000, Cosmic Research

  3. Malignant peripheral nerve sheath tumour of penis.

    PubMed

    Kaur, J; Madan, R; Singh, L; Sharma, D N; Julka, P K; Rath, G K; Roy, S

    2015-04-01

    Malignant peripheral nerve sheath tumour (MPNST) is a rare variety of soft tissue sarcoma that originates from Schwann cells or pluripotent cells of neural crest origin. They have historically been difficult tumours to diagnose and treat. Surgery is the mainstay of treatment with a goal to achieve negative margins. Despite aggressive surgery and adjuvant therapy, the prognosis of patients with MPNST remains poor. MPNST arising from penis is a very rare entity; thus, it presents a diagnostic and therapeutic challenge. We present a case of penile MPNST in a 38-year-old man in the absence of neurofibromatosis treated with surgery followed by post-operative radiotherapy to a dose of 60 Gray in 30 fractions and adjuvant chemotherapy with ifosfamide and adriamycin.

  4. Effect of total emitted electron velocity distribution function on the plasma sheath near a floating wall

    NASA Astrophysics Data System (ADS)

    Qing, Shaowei; Hu, Zhou

    2017-08-01

    Electrons emitted from a solid surface can noticeably affect characteristics of plasma sheath surrounding that surface by modifying current balance at wall, charge separation in sheath region and Bohm criterion at sheath edge. We establish a static sheath model with kinetic electrons and cold ions to emphasize the effect of different total emitted electron velocity distribution functions (EEVDFs) on classic sheath solution and its structure transition. Four total EEVDFs with same average energy are considered separately. It is found that total EEVDFs influence the sheath solution and the threshold of total electron emission coefficient (EEC) for classic sheath dramatically, and can cause no solution for critical space-charge limited (SCL) sheath. These results indicate that, as EEC increases from zero gradually, the sheath will not transit from classic sheath to SCL sheath structure for some special total EEVDFs.

  5. Morphogenesis of the fibrous sheath in the marsupial spermatozoon.

    PubMed

    Ricci, M; Breed, W G

    2005-08-01

    The spermatozoon fibrous sheath contains longitudinal columns and circumferential ribs. It surrounds the axoneme of the principal piece of the mammalian sperm tail, and may be important in sperm stability and motility. Here we describe its assembly during spermiogenesis in a marsupial, the brush-tail possum, and compare its structural organization with that of eutherian mammals, birds and reptiles. Transmission electron microscopy showed that possum fibrous sheath assembly is a multistep process extending in a distal-to-proximal direction along the axoneme from steps 4 to 14 of spermiogenesis. For the most part, assembly of the longitudinal columns occurs before that of the circumferential ribs. Immunohistochemical and immunogold labelling showed that fibrous sheath proteins are first present in the spermatid cytoplasm; at least some of the proteins of the sheath precursors differ from those in the mature fibrous sheath. That immunoreactivity develops after initiation of chromatin condensation suggests that fibrous sheath proteins, or their mRNAs, are stored within the spermatid cytoplasmic lobule prior to their assembly along the axoneme. These findings are similar to those in laboratory rats, and thus suggests that the mode of fibrous sheath assembly evolved in a common ancestor over 125 million years ago, prior to the divergence of marsupial and eutherian lineages.

  6. Molecular architecture of the sheathed polar flagellum in Vibrio alginolyticus.

    PubMed

    Zhu, Shiwei; Nishikino, Tatsuro; Hu, Bo; Kojima, Seiji; Homma, Michio; Liu, Jun

    2017-09-25

    Vibrio species are Gram-negative rod-shaped bacteria that are ubiquitous and often highly motile in aqueous environments. Vibrio swimming motility is driven by a polar flagellum covered with a membranous sheath, but this sheathed flagellum is not well understood at the molecular level because of limited structural information. Here, we use Vibrio alginolyticus as a model system to study the sheathed flagellum in intact cells by combining cryoelectron tomography (cryo-ET) and subtomogram analysis with a genetic approach. We reveal striking differences between sheathed and unsheathed flagella in V. alginolyticus cells, including a novel ring-like structure at the bottom of the hook that is associated with major remodeling of the outer membrane and sheath formation. Using mutants defective in flagellar motor components, we defined a Vibrio-specific feature (also known as the T ring) as a distinctive periplasmic structure with 13-fold symmetry. The unique architecture of the T ring provides a static platform to recruit the PomA/B complexes, which are required to generate higher torques for rotation of the sheathed flagellum and fast motility of Vibrio cells. Furthermore, the Vibrio flagellar motor exhibits an intrinsic length variation between the inner and the outer membrane bound complexes, suggesting the outer membrane bound complex can shift slightly along the axial rod during flagellar rotation. Together, our detailed analyses of the polar flagella in intact cells provide insights into unique aspects of the sheathed flagellum and the distinct motility of Vibrio species.

  7. Nonextensive statistics and the sheath criterion in collisional plasmas

    SciTech Connect

    Hatami, M. M.

    2015-01-15

    The Bohm criterion in an electropositive plasma containing nonextensively distributed electrons and warm ions is investigated by using a steady state two-fluid model. Taking into account the ion-neutral collisions and finite temperature of ions, a modified Bohm criterion is derived which limits both maximum and minimum allowable velocity of ions at the sheath edge (u{sub 0i}). It is found that the degree of nonextensivity of electrons (q) and temperature of positive ions (T{sub i}) affect only the lower limit of the entrance velocity of ions into the sheath while the degree of ion collisionality (α) influences both lower and upper limits of the ion velocities at the sheath edge. In addition, depending on the value of q, it is shown that the minimum velocity of positive ions at the sheath edge can be greater or smaller than its Maxwellian counterpart. Moreover, it is shown that, depending on the values of α and T{sub i}, the positive ions with subsonic velocity may enter the sheath for either q > 1 or −1 < q < 1. Finally, as a practical application, the density distribution of charged particles in the sheath region is studied for different values of u{sub 0i}, and it is shown that monotonical reduction of the positive ion density distribution occurs only when the velocity of positive ions at the sheath edge lies between two above mentioned limits.

  8. Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths.

    PubMed

    Kunoh, Tatsuki; Hashimoto, Hideki; McFarlane, Ian R; Hayashi, Naoaki; Suzuki, Tomoko; Taketa, Eisuke; Tamura, Katsunori; Takano, Mikio; El-Naggar, Mohamed Y; Kunoh, Hitoshi; Takada, Jun

    2016-06-03

    Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths.

  9. Morphogenesis of the fibrous sheath in the marsupial spermatozoon

    PubMed Central

    Ricci, M; Breed, WG

    2005-01-01

    The spermatozoon fibrous sheath contains longitudinal columns and circumferential ribs. It surrounds the axoneme of the principal piece of the mammalian sperm tail, and may be important in sperm stability and motility. Here we describe its assembly during spermiogenesis in a marsupial, the brush-tail possum, and compare its structural organization with that of eutherian mammals, birds and reptiles. Transmission electron microscopy showed that possum fibrous sheath assembly is a multistep process extending in a distal-to-proximal direction along the axoneme from steps 4 to 14 of spermiogenesis. For the most part, assembly of the longitudinal columns occurs before that of the circumferential ribs. Immunohistochemical and immunogold labelling showed that fibrous sheath proteins are first present in the spermatid cytoplasm; at least some of the proteins of the sheath precursors differ from those in the mature fibrous sheath. That immunoreactivity develops after initiation of chromatin condensation suggests that fibrous sheath proteins, or their mRNAs, are stored within the spermatid cytoplasmic lobule prior to their assembly along the axoneme. These findings are similar to those in laboratory rats, and thus suggests that the mode of fibrous sheath assembly evolved in a common ancestor over 125 million years ago, prior to the divergence of marsupial and eutherian lineages. PMID:16050902

  10. The plasma drag and dust motion inside the magnetized sheath

    SciTech Connect

    Pandey, B. P.; Vladimirov, S. V.; Samarian, A.

    2011-05-15

    The motion of micron size dust inside the sheath in the presence of an oblique magnetic field is investigated by self-consistently calculating the charge and various forces acting on the dust. It is shown that the dust trajectory inside the sheath, which is like an Archimedean spiral swinging back and forth between the wall and the plasma-sheath boundary, depends only indirectly on the orientation of the magnetic field. When the Lorentz force is smaller than the collisional momentum exchange, the dust dynamics is insensitive to the obliqueness of the magnetic field. Only when the magnetic field is strong enough, the sheath structure and, thus, the dust dynamics are significantly affected by the field orientation. Balance between the plasma drag, sheath electrostatic field, and gravity plays an important role in determining how far the dust can travel inside the sheath. The dust equilibrium point shifts closer to the wall in the presence of gravity and plasma drag. However, in the absence of plasma drag, dust can sneak back into the plasma if acted only by gravity. The implication of our results to the usability of dust as a sheath probe is discussed.

  11. Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

    PubMed Central

    Kunoh, Tatsuki; Hashimoto, Hideki; McFarlane, Ian R.; Hayashi, Naoaki; Suzuki, Tomoko; Taketa, Eisuke; Tamura, Katsunori; Takano, Mikio; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths. PMID:27271677

  12. Rectus sheath haematoma: a rare masquerader for abdominal pain.

    PubMed

    Changal, Khalid Hamid; Saleem, Saad; Ghous, Ghulam

    2017-04-13

    Rectus sheath haematoma is a rare cause of abdominal pain. It can be easily confused for other causes of acute abdomen and may even lead to unnecessary laparotomies. Our patient has the rectus sheath haematoma because of violent coughing and on presentation had no obvious clinical sign pointing to the same. Diagnosis was made by a CT scan of the abdomen, and patient was treated conservatively. Rectus sheath haematomas are usually present on the posterior aspect of the rectus muscles and thus may not be clinically appreciable.

  13. Absence of Debye Sheaths Due to Secondary Electron Emission

    SciTech Connect

    M.D. Campanell, A. Khrabrov and I. D. Kaganovich

    2012-05-11

    A bounded plasma where the hot electrons impacting the walls produce more than one secondary on average is studied via particle-in-cell simulation. It is found that no classical Debye sheath or space-charge limited sheath exists. Ions are not drawn to the walls and electrons are not repelled. Hence the unconfined plasma electrons travel unobstructed to the walls, causing extreme particle and energy fluxes. Each wall has a positive charge, forming a small potential barrier or "inverse sheath" that pulls some secondaries back to the wall to maintain the zero current condition.

  14. Analytical model for the radio-frequency sheath.

    PubMed

    Czarnetzki, Uwe

    2013-12-01

    A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary

  15. Analytical model for the radio-frequency sheath

    NASA Astrophysics Data System (ADS)

    Czarnetzki, Uwe

    2013-12-01

    A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary

  16. Measurement of sheath thickness at a floating potential

    SciTech Connect

    Han, Hyung-Sik; Lee, Hyo-Chang; Oh, Se-Jin; Chung, Chin-Wook

    2014-02-15

    In a cylindrical Langmuir probe measurement, ion current is collected from the surface of the sheath surrounded at probe tip, not at the surface of the probe tip. By using this, the sheath thickness can be obtained, if we know some unknown parameters, such as ion current, plasma density, and electron temperature. In this paper, we present a method to measure sheath thickness by using a wave cutoff method and a floating harmonic method. The measured result is in a good agreement with Allen-Boyd-Reynolds theory.

  17. 32. DETAIL OF GEARS LOOKING NORTH WITH SHEATHING REMOVED AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    32. DETAIL OF GEARS LOOKING NORTH WITH SHEATHING REMOVED AND SHAFT OF KING GEAR BEYOND - Caleb Crosby Threshing Barn, Noeton (moved to Norris Dam State Park, Lake City), Morristown, Hamblen County, TN

  18. Stability of the Tonks–Langmuir discharge pre-sheath

    SciTech Connect

    Tskhakaya, D. D.; Kos, L.; Tskhakaya, D.

    2016-03-15

    The article formulates the stability problem of the plasma sheath in the Tonks–Langmuir discharge. Using the kinetic description of the ion gas, i.e., the stability of the potential shape in the quasi-neutral pre-sheath regarding the high and low frequency, the perturbations are investigated. The electrons are assumed to be Maxwell–Boltzmann distributed. Regarding high-frequency perturbations, the pre-sheath is shown to be stable. The stability problem regarding low-frequency perturbations can be reduced to an analysis of the “diffusion like” equation, which results in the instability of the potential distribution in the pre-sheath. By means of the Particle in Cell simulations, also the nonlinear stage of low frequency oscillations is investigated. Comparing the figure obtained with the figure for linear stage, one can find obvious similarity in the spatial-temporal behavior of the potential.

  19. A radio-frequency sheath model for complex waveforms

    SciTech Connect

    Turner, M. M.; Chabert, P.

    2014-04-21

    Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

  20. Flexor Tendon Sheath Engineering Using Decellularized Porcine Pericardium.

    PubMed

    Megerle, Kai; Woon, Colin; Kraus, Armin; Raghavan, Shyam; Pham, Hung; Chang, James

    2016-10-01

    The flexor tendon sheath is an ideal target for tissue engineering because it is difficult to reconstruct by conventional surgical methods. The authors hypothesized that decellularized porcine pericardium can be used as a scaffold for engineering a biologically active tendon sheath. The authors' protocol removed cellular material from the pericardium and preserved the structural architecture in addition to the collagen and glycosaminoglycan content. The scaffold was successfully reseeded with human sheath synoviocytes and human adipose-derived stem cells. Cells were evaluated for 8 weeks after reseeding. The reseeded construct demonstrated continuous production of hyaluronic acid, the main component of synovial fluid. After being seeded on the membrane, adipose-derived stem cells demonstrated down-regulation of collagen I and III and up-regulation of hyaluronan synthase 2. The results indicate that decellularized porcine pericardium may be a potential scaffold for engineering a biologically active human tendon sheath.

  1. Porous protective solid phase micro-extractor sheath

    DOEpatents

    Andresen, Brian D.; Randich, Erik

    2005-03-29

    A porous protective sheath for active extraction media used in solid phase microextraction (SPME). The sheath permits exposure of the media to the environment without the necessity of extending a fragile coated fiber from a protective tube or needle. Subsequently, the sheath can pierce and seal with GC-MS septums, allowing direct injection of samples into inlet ports of analytical equipment. Use of the porous protective sheath, within which the active extraction media is contained, mitigates the problems of: 1) fiber breakage while the fiber is extended during sampling, 2) active media coating loss caused by physical contact of the bare fiber with the sampling environment; and 3) coating slough-off during fiber extension and retraction operations caused by rubbing action between the fiber and protective needle or tube.

  2. Melanocytic Malignant Peripheral Nerve Sheath Tumor of the Male Breast.

    PubMed

    Wang, Haijun; Ge, Jing; Chen, Lirong; Xie, Panpan; Chen, Fangfang; Chen, Yiding

    2009-01-01

    SUMMARY: BACKGROUND: Malignant peripheral nerve sheath tumors are rare tumor entities that originate from peripheral nerve sheaths and have an unfavorable prognosis. Common sites include deeper soft tissues, usually in the proximity of a nerve trunk. Breast is an absolutely rare location of this lesion, and presentation as a breast lump in the male breast is even rarer. CASE REPORT: A 65-year-old man presented with a 6-month history of a painless mass of the left breast. Tissue biopsy was performed. Histopathology revealed a malignant spindle cell tumor which was confirmed to be a melanocytic malignant peripheral nerve sheath tumor on the basis of immunopositivity for HMB45 and S-100. CONCLUSION: There are no generally accepted guidelines for the treatment of malignant peripheral nerve sheath tumors in the male breast. The patient was referred for radiation therapy after simple mastectomy.

  3. Detail of trusses and wood sheathing in the leanto bay ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of trusses and wood sheathing in the lean-to bay of the roundhouse and car repair shop looking north. - U.S. Steel National Tube Works, Auxiliary Buildings, Along Monongahela River, McKeesport, Allegheny County, PA

  4. Measure Guideline: Guidance on Taped Insulating Sheathing Drainage Planes

    SciTech Connect

    Grin, A.; Lstiburek, J.

    2014-09-01

    The goal of this research is to provide durable and long-term water management solutions using exterior insulating sheathing as part of the water management system. It is possible to tape or seal the joints in insulating sheathing to create a drainage plane and even an air control layer. There exists the material durability component of the tape as well as the system durability component being the taped insulating sheathing as the drainage plane. This measure guideline provides best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience. Three significant issues were discussed with the group, which are required to make taped insulating sheathing a simple, long-term, and durable drainage plane: horizontal joints should be limited or eliminated wherever possible; where a horizontal joint exists use superior materials; and frequent installation inspection and regular trade training are required to maintain proper installation.

  5. Use of a straight, side-hole delivery sheath for improved delivery of Amplatzer ASD occluder.

    PubMed

    Kutty, Shelby; Asnes, Jeremy D; Srinath, Gowdagere; Preminger, Tamar J; Prieto, Lourdes R; Latson, Larry A

    2007-01-01

    The Amplatzer ASD occluder may be difficult to position in some patients with a large atrial septal defect (ASD) or deficiency of one or more atrial septal rims. We developed a method to modify a Mullins transseptal sheath to enhance delivery. The resulting sheath is straight and has an exit orifice essential in the side of the distal portion of the sheath-a straight, side-hole (SSH) delivery sheath. We have used this modified delivery sheath in 140 successive patients with excellent results. The techniques of sheath modification and delivery of the device using the modified sheath are described.

  6. Sheath ionization model of beam emissions from large spacecraft

    NASA Technical Reports Server (NTRS)

    Lai, S. T.; Cohen, H. A.; Bhavnani, K. H.; Tautz, M. E.

    1985-01-01

    An analytical model of the charging of a spacecraft emitting electron and ion beams has been applied to the case of large spacecraft. In this model, ionization occurs in the sheath due to the return current. Charge neutralization of spherical space charge flow is examined by solving analytical equations numerically. Parametric studies of potential large spacecraft are performed. As in the case of small spacecraft, the ions created in the sheath by the returning current play a large role in determining spacecraft potential.

  7. Insulating and cooling effects of nasal endoscope sheaths and irrigation.

    PubMed

    Craig, John; Goyal, Parul

    2014-09-01

    Heat generated at the tips of nasal endoscopes have been shown to reach temperatures high enough to cause thermal tissue injury. Endoscope sheaths have the potential to minimize the risk of thermal tissue injury. The purpose of this study was to assess the abilities of plastic and metal endoscope sheaths and sheath irrigation to insulate against dangerous scope tip temperatures. A 4-mm 0-degree rigid nasal endoscope was used with light-emitting diode (LED) and xenon light sources (400-W LED, 300-W, and 175-W xenon) to assess scope tip temperature before and after endoscope sheath placement. Temperatures were assessed again after placement of each sheath, both before and after active saline irrigation. Scope tip temperature was measured using a noncontact infrared thermometer. The unsheathed rigid scope tip reached a maximal temperature after 10 minutes at 100% light source intensity. The 400-W LED and 300-W xenon sources generated potentially dangerous scope tip temperatures exceeding 42°C, whereas the 175-W xenon source never generated a maximal temperature over 32.6°C. After placement of plastic and metal sheaths, mean scope tip temperatures were decreased by 2°C (4.8%) and 2.2°C (5.5%), respectively. After active saline irrigation, mean scope tip temperatures were decreased by 5.1°C (12.6%) and 5.2°C (12.8%), respectively. With modern light sources, nasal endoscopes have the potential to reach temperatures that may cause thermal tissue injury. Endoscope sheaths lead to decreases in scope temperatures, and the effect is greater with active irrigation. In addition to improving visualization, endoscope sheaths may decrease the risk of thermal tissue injury. © 2014 ARS-AAOA, LLC.

  8. Solitary fibrous tumor surrounding the carotid sheath.

    PubMed

    Gómez-Oliveira, Guillermo; Alvarez-Flores, Modesto; Arribas-García, Ignacio; Martínez-Gimeno, Carlos

    2010-03-01

    Solitary fibrous tumors (SFTs) are rare spindle cell neoplasms that are mostly found arising from the pleura. Although SFTs recently have been reported in other regions, they are rare in the head and neck and have often been misdiagnosed due to their rarity. SFTs are benign in most cases. Clinically, SFTs usually manifest as well-circumscribed, slow-growing, smooth and painless masses. Symptoms are often minimal, although they may include sore throat, difficulty in swallowing, change of voice or trismus. CT-Scan and MRI are the most sensitive imaging procedures used. The treatment of choice is complete surgical excision of the lesion. Because recurrences have been noted up to 30 years after surgery, long-term follow up is mandatory. In this article, we present a case of a Solitary Fibrous Tumor arising in the parapharyngeal space in a 20-year-old man, involving the carotid sheath, treated by surgical excision with no recurrence after 1 year. The clinical presentation, surgical management and pathological findings are described.

  9. Rectus sheath tunnels for continent stomas.

    PubMed

    Dickson, Alan P; Khalil, Basem A; Cervellione, Raimondo M

    2008-03-01

    Continent stoma rectus sheath tunnel (CSRST) has been used in antegrade colonic enema (ACE) and urinary continent cutaneous diversion (UCCD) stomas to reduce leakage and to support a straight track for the continent conduit. All patients that underwent CSRST between 1995 and 2005 were identified and their case notes retrospectively reviewed. Patients were divided into two groups: the ACE group and the UCCD group. Demographic data, age at surgery and complications including stenosis and leakage were recorded. Forty patients underwent CSRST between 1995 and 2005. The mean age and standard deviation (SD) at surgery was 6.8 (2.1) years. Eighteen patients underwent ACE with a mean (SD) follow-up of 7.6 (3.1) years. No patient has faecal leakage. No patient had stomal revision, but one patient (5.5%) required an indwelling gastrostomy button to maintain patency. Twenty-two patients underwent UCCD with a mean (SD) follow-up of 8.1 (2.8) years. No patient developed urinary leakage. Two patients (9%) required revision of the stoma and one (4.5%) required an indwelling catheter because of recurring stomal stenosis. CSRST prevents stoma leakage. Revision surgery rate after CSRST is low, particularly after ACE reconstruction.

  10. A Coupled Plasma and Sheath Model for High Density Reactors

    NASA Technical Reports Server (NTRS)

    Deepak, Bose; Govindan, T. R.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2001-01-01

    We present a coupled plasma and collisionless; sheath model for the simulation of high density plasma processing reactors. Due to inefficiencies in numerical schemes and the resulting computational burden, a coupled multidimensional plasma and sheath simulation has not been possible model for gas mixtures and high density reactors of practical interest. In this work we demonstrate that with a fully implicit algorithm and a refined computational mesh, a self-consistent plasma and sheath simulation is feasible. We discuss the details of the model equations, the importance of ion inertia, and the resulting sheath profiles for argon and chlorine plasmas. We find that at low operating pressures (10-30 mTorr), the charge separation occurs only within a 0.5 mm layer near the surface in a 300 mm inductively coupled plasma etch reactor. A unified model eliminates the use of off-line or loosely coupled sheath models with simplifying assumptions which generally lead to uncertainties in ion flux and sheath electrical properties.

  11. Boundary conditions for electropositive and electronegative radio-frequency sheaths

    NASA Astrophysics Data System (ADS)

    Sobolewski, Mark

    2016-09-01

    Plasma sheaths play a dominant role in determining ion bombardment energies. To optimize plasma processes, sheaths must be understood and carefully controlled, which requires predictive models. One very efficient approach is to only model the sheath, excluding the bulk plasma. This approach, however, requires boundary conditions at the plasma/sheath boundary. Models that use the step approximation for electron density require initial ion velocities. More exact models with Boltzmann electrons (and, for electronegative discharges, negative ions) require the electron temperature (and the temperature and relative density of negative ions). It is often assumed that these boundary conditions have negligible effects on ion energies, but, for certain conditions in radio-frequency sheaths, this is not true. Analytic models as well as numerical simulations show that, at low frequencies (<= 1 MHz) and high bias voltages, the amplitude of the low-energy peak in ion energy distributions (IEDs) at the electrode is very sensitive to the boundary conditions. By measuring IEDs and sheath voltage waveforms, we obtain the most appropriate values of the boundary conditions for electropositive (Ar) as well as electronegative (CF4) discharges and insight into their presheath dynamics.

  12. Structure of the magnetized sheath of a dusty plasma

    SciTech Connect

    Mehdipour, H.; Denysenko, I.; Ostrikov, K.

    2010-12-15

    A three-component fluid model for a dusty plasma-sheath in an oblique magnetic field is presented. The study is carried out for the conditions when the thermophoretic force associated with the electron temperature gradient is one of the most important forces affecting dust grains in the sheath. It is shown that the sheath properties (the sheath size, the electron, ion and dust particle densities and velocities, the electric field potential, and the forces affecting the dust particles) are functions of the neutral gas pressure and ion temperature, the dust size, the dust material density, and the electron temperature gradient. Effects of plasma-dust collisions on the sheath structure are studied. It is shown that an increase in the forces pushing dust particles to the wall is accompanied by a decrease in the sheath width. The results of this work are particularly relevant to low-temperature plasma-enabled technologies, where effective control of nano- and microsized particles near solid or liquid surfaces is required.

  13. The sheath effect on the floating harmonic method

    SciTech Connect

    Lee, Jaewon; Kim, Kyung-Hyun; Chung, Chin-Wook

    2015-12-15

    The floating harmonic method biases sinusoidal voltage to a probe sheath, and as its response, harmonic currents can be obtained. These currents can be used to determine the plasma parameters. However, different shapes of probes have different shapes of sheaths that can affect the diagnostic results. However, no research has been done on the sheath effect on the floating harmonic method. Therefore, we investigate the effect of the sheath during floating harmonic diagnostics by comparing cylindrical and planar probes. While the sinusoidal voltages were applied to a probe, because the sheath oscillated, the time variant ion current and their harmonic currents were added to the electron harmonic currents. In the floating harmonic method, the harmonic currents are composed of only the electron harmonic currents. Therefore, the ion harmonic currents affect the diagnostic results. In particular, the electron temperature obtained by the small probe tip was higher than that of the large probe tip. This effect was exacerbated when the ratio of the probe tip radius to the sheath length was smaller.

  14. Photoelectric sheath formation around small spherical objects in space

    SciTech Connect

    Misra, Shikha Sodha, M. S.; Mishra, S. K.

    2015-04-15

    The formation of a photoelectron sheath around positively charged small (∼cm) spherical objects roaming in near earth space due to the solar radiation (with continuous spectrum) and the solar wind plasma has been investigated. The sheath structure has been derived, taking into account anisotropic photoelectron flux with the Poisson equation, spherical geometry of the object, and half Fermi Dirac distribution of photoelectron velocities. Two cases, viz., when the object is illuminated by (i) isotropic or (ii) unidirectional (parallel beam) radiation, have been analyzed. The analysis predicts a spherically symmetric sheath in case of isotropic illumination, while a symmetry in sheath about a θ=π/4 is seen in case of parallel beam illumination; θ is the angle of incidence which is the angle made by the normal to a surface element with the direction of incidence of solar radiation. The radial and angular profiles of the electric potential and electron density in the photoelectron sheath have been evaluated and illustrated graphically; the dependence of the sheath structure on the solar wind plasma parameters, material properties of the spherical object, and its size have been discussed.

  15. Comment on 'Sheath model for dual-frequency capacitive discharges'

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Cong; Pu, Yi-Kang

    2015-07-01

    Boyle et al (2004 J. Phys. D: Appl. Phys. 37 1451) introduced a sheath model for dual-frequency capacitive discharges. The electron sheath edge position s and the dc potential Φdc in the sheath are obtained with the assumption α/β  >> 1 (where α/β is the ratio of the low-frequency electric field to the high-frequency electric field). However, α/β  ≤  4 is usually found in processing applications. Under this condition, we show that the Boyle et al model gives multiple values for the dc potential Φdc(x) at any given position x in the sheath. For this reason, we introduce a model without the assumption α/β  >> 1. By comparing the results from the two models, it is found that, as the ratio α/β approaches 1, the sheath thickness sm and the sheath dc voltage Vdc obtained with the Boyle et al model are significantly underestimated.

  16. Application of the physics of plasma sheaths to the modeling of RF plasma reactors

    NASA Astrophysics Data System (ADS)

    Metze, A.; Ernie, D. W.; Oskam, H. J.

    1986-11-01

    An equivalent circuit model is presented for a planar RF plasma reactor. The physical properties of the plasma sheath adjacent to the electrodes are incorporated in the model. The sheath capacitances and the conduction currents through the sheaths are time varying and have a highly nonlinear dependence on the potentials across the plasma sheaths. The model shows that the waveforms of the voltage differences across the sheaths are highly nonsinusoidal and agree with reported measurements.

  17. Laser Diagnostic Method for Plasma Sheath Potential Mapping

    NASA Astrophysics Data System (ADS)

    Walsh, Sean P.

    Electric propulsion systems are gaining popularity in the aerospace field as a viable option for long term positioning and thrusting applications. In particular, Hall thrusters have shown promise as the primary propulsion engine for space probes during interplanetary journeys. However, the interaction between propellant xenon ions and the ceramic channel wall continues to remain a complex issue. The most significant source of power loss in Hall thrusters is due to electron and ion currents through the sheath to the channel wall. A sheath is a region of high electric field that separates a plasma from a wall or surface in contact. Plasma electrons with enough energy to penetrate the sheath may result emission of a secondary electron from the wall. With significant secondary electron emission (SEE), the sheath voltage is reduced and so too is the electron retarding electric field. Therefore, a lower sheath voltage further increases the particle loss to the wall of a Hall thruster and leads to plasma cooling and lower efficiency. To further understand sheath dynamics, laser-induced fluorescence is employed to provide a non-invasive, in situ, and spatially resolved technique for measuring xenon ion velocity. By scanning the laser wavelength over an electronic transition of singly ionized xenon and collecting the resulting fluorescence, one can determine the ion velocity from the Doppler shifted absorption. Knowing the velocity at multiple points in the sheath, it can be converted to a relative electric potential profile which can reveal a lot about the plasma-wall interaction and the severity of SEE. The challenge of adequately measuring sheath potential profiles is optimizing the experiment to maximize the signal-to-noise ratio. A strong signal with low noise, enables high resolution measurements and increases the depth of measurement in the sheath, where the signal strength is lowest. Many improvements were made to reduce the background luminosity, increase the

  18. A theoretical model of sheath fold morphology in simple shear

    NASA Astrophysics Data System (ADS)

    Reber, Jacqueline E.; Dabrowski, Marcin; Galland, Olivier; Schmid, Daniel W.

    2013-04-01

    Sheath folds are highly non-cylindrical structures often associated with shear zones. The geometry of sheath folds, especially cross-sections perpendicular to the stretching direction that display eye-patterns, have been used in the field to deduce kinematic information such as shear sense and bulk strain type. However, how sheath folds form and how they evolve with increasing strain is still a matter of debate. We investigate the formation of sheath folds around a weak inclusion acting as a slip surface in simple shear by means of an analytical model. We systematically vary the slip surface orientation and shape and evaluate the impact on the evolving eye-pattern. In addition we compare our results to existing classifications. Based on field observations it has been suggested that the shear sense of a shear zone can be determined by knowing the position of the center of an eye-pattern and the closing direction of the corresponding sheath fold. In our modeled sheath folds we can observe for a given strain that the center of the eye-structure is subject to change in height with respect to the upper edge of the outermost closed contour for different cross-sections perpendicular to the shear direction. This results in a large variability in layer thickness, questioning the usefulness of sheath folds as shear sense indicators. The location of the center of the eye structure, however, is largely invariant to the initial configurations of the slip surface as well as to strain. It has been suggested that the ratio of the aspect ratio of the innermost and outermost closed contour in eye-patterns could be linked to the bulk strain type based on filed observations. We apply this classification to our modeled sheath folds and we observe that the values of the aspect ratios of the closed contours within the eye-pattern are dependent on the strain and the cross-section location. The ratio (R') of the aspect ratios of the outermost closed contour (Ryz) and the innermost closed

  19. Ion Velocimetry In Magnetized DC Sheaths

    NASA Astrophysics Data System (ADS)

    Young, Christopher; Lucca Fabris, Andrea; Cappelli, Mark

    2013-09-01

    Particle dynamics near the magnetic cusps in cusped field plasma thrusters are still not well understood; characterizing the ion velocity distribution functions in these regions can help thruster designs maximize electron trapping and minimize erosion of the channel wall. To that end, a robust argon ion velocity sensor is developed using a three-level laser-induced fluorescence (LIF) technique. The 3d4F7 / 2 --> 4p4D5/ 2 0 ArII transition at 668.61 nm is pumped with a 25 mW tunable external cavity diode laser, and fluorescence down to the 4s4P3 / 2 state at 442.72 nm is collected with phase-sensitive detection. The Doppler shift in the acquired signal peak, compared to a stationary reference, gives the ion velocity component parallel to the exciting laser. We demonstrate this LIF scheme by obtaining the argon ion velocity profile through a magnetized DC sheath. The LIF measurement is used to validate a new optogalvanic velocimetry technique in which two lasers (chopped at different frequencies) intersect one another at 90° in the measurement volume. Using a lock-in amplifier, changes observed in the DC discharge current at the sum and difference of the two chopping frequencies may be related back to the mean ion velocity at that point. The authors acknowledge support from the Air Force Office of Scientific Research (AFOSR). CY acknowledges support from the DOE NNSA Stewardship Science Graduate Fellowship under contract DE-FC52-08NA28752.

  20. On the usefulness of sheath folds as kinematic indicators

    NASA Astrophysics Data System (ADS)

    Reber, J. E.; Galland, O.; Dabrowski, M.; Schmid, D. W.; Cobbold, P. R.

    2012-04-01

    Sheath folds are cone-shaped structures that can be found in different rock types. They are mostly associated with shear zones. Even though they are three-dimensional structures they are most commonly recognized in nature in cross sections perpendicular to their stretching direction. These cross-sections exhibit so called eye-structures. The geometry of sheath folds has been used to deduce kinematic information such as strain, shear sense, and bulk strain type. However, how sheath folds form and how they evolve with increasing strain is still a matter of debate. We studied the development of sheath folds at the tip of a slip surface (weak inclusion) embedded in a layered matrix subjected to simple shear by means of analytical and experimental modeling. With this combined approach we tested the usefulness of sheath folds as indicators of strain, shear direction and bulk strain type. The analytical model is three-dimensional and based on an adapted external Eshelby solution. The slip surface is embedded in a homogeneous matrix, which is subjected to simple shear. Layers are introduced as passive markers for the visualization. With this method we tested the influence of the initial slip surface orientation (0°, 90°, or 135° with respect to the shear direction) and the number of layers on the evolving eye-structure. To study the effect of mechanical layering (viscosity contrast, layer thickness) on the geometry of the eye-structures we designed an experimental model using silicones as rock analogues. Although sheath folds are commonly considered as high strain markers, the analytical model shows that very little strain is needed to produce a sheath fold and the corresponding eye-pattern, and that the minimum strain is mainly dependent on the orientation of the slip surface and the number of layers. Our analytical as well as the experimental models revealed a sheath fold at both tips of the deformed slip surface. The two sheath folds show opposing closing direction

  1. Structural Conservation of the Myoviridae Phage Tail Sheath Protein Fold

    SciTech Connect

    Aksyuk, Anastasia A.; Kurochkina, Lidia P.; Fokine, Andrei; Forouhar, Farhad; Mesyanzhinov, Vadim V.; Tong, Liang; Rossmann, Michael G.

    2012-02-21

    Bacteriophage phiKZ is a giant phage that infects Pseudomonas aeruginosa, a human pathogen. The phiKZ virion consists of a 1450 {angstrom} diameter icosahedral head and a 2000 {angstrom}-long contractile tail. The structure of the whole virus was previously reported, showing that its tail organization in the extended state is similar to the well-studied Myovirus bacteriophage T4 tail. The crystal structure of a tail sheath protein fragment of phiKZ was determined to 2.4 {angstrom} resolution. Furthermore, crystal structures of two prophage tail sheath proteins were determined to 1.9 and 3.3 {angstrom} resolution. Despite low sequence identity between these proteins, all of these structures have a similar fold. The crystal structure of the phiKZ tail sheath protein has been fitted into cryo-electron-microscopy reconstructions of the extended tail sheath and of a polysheath. The structural rearrangement of the phiKZ tail sheath contraction was found to be similar to that of phage T4.

  2. Sheath-accumulating Propagation of Interplanetary Coronal Mass Ejection

    NASA Astrophysics Data System (ADS)

    Takahashi, Takuya; Shibata, Kazunari

    2017-03-01

    Fast interplanetary coronal mass ejections (ICMEs) are the drivers of strong space weather storms such as solar energetic particle events and geomagnetic storms. The connection between the space-weather-impacting solar wind disturbances associated with fast ICMEs at Earth and the characteristics of causative energetic CMEs observed near the Sun is a key question in the study of space weather storms, as well as in the development of practical space weather prediction. Such shock-driving fast ICMEs usually expand at supersonic speeds during the propagation, resulting in the continuous accumulation of shocked sheath plasma ahead. In this paper, we propose a “sheath-accumulating propagation” (SAP) model that describes the coevolution of the interplanetary sheath and decelerating ICME ejecta by taking into account the process of upstream solar wind plasma accumulation within the sheath region. Based on the SAP model, we discuss (1) ICME deceleration characteristics; (2) the fundamental condition for fast ICMEs at Earth; (3) the thickness of interplanetary sheaths; (4) arrival time prediction; and (5) the super-intense geomagnetic storms associated with huge solar flares. We quantitatively show that not only the speed but also the mass of the CME are crucial for discussing the above five points. The similarities and differences between the SAP model, the drag-based model, and the“snow-plow” model proposed by Tappin are also discussed.

  3. Ontogeny of the sheathing leaf base in maize (Zea mays).

    PubMed

    Johnston, Robyn; Leiboff, Samuel; Scanlon, Michael J

    2015-01-01

    Leaves develop from the shoot apical meristem (SAM) via recruitment of leaf founder cells. Unlike eudicots, most monocot leaves display parallel venation and sheathing bases wherein the margins overlap the stem. Here we utilized computed tomography (CT) imaging, localization of PIN-FORMED1 (PIN1) auxin transport proteins, and in situ hybridization of leaf developmental transcripts to analyze the ontogeny of monocot leaf morphology in maize (Zea mays). CT imaging of whole-mounted shoot apices illustrates the plastochron-specific stages during initiation of the basal sheath margins from the tubular disc of insertion (DOI). PIN1 localizations identify basipetal auxin transport in the SAM L1 layer at the site of leaf initiation, a process that continues reiteratively during later recruitment of lateral leaf domains. Refinement of these auxin transport domains results in multiple, parallel provascular strands within the initiating primordium. By contrast, auxin is transported from the L2 toward the L1 at the developing margins of the leaf sheath. Transcripts involved in organ boundary formation and dorsiventral patterning accumulate within the DOI, preceding the outgrowth of the overlapping margins of the sheathing leaf base. We suggest a model wherein sheathing bases and parallel veins are both patterned via the extended recruitment of lateral maize leaf domains from the SAM. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  4. Revisiting the plasma sheath—dust in plasma sheath

    NASA Astrophysics Data System (ADS)

    Das, G. C.; Deka, R.; Bora, M. P.

    2016-04-01

    In this work, we have considered the formation of warm plasma sheath in the vicinity of a wall in a plasma with considerable presence of dust particles. As an example, we have used the parameters relevant in case of plasma sheath formed around surfaces of various solid bodies in space, though the results obtained in this work can be applied to any other physical situation such as laboratory plasma. In the ion-acoustic time scale, we neglect the dust dynamics. The dust particles affect the sheath dynamics by affecting the Poisson equation which determines the plasma potential in the sheath region. It is important to note that our calculations are valid only when the amount of dust particles is not sufficient so as to affect the plasma dynamics in the dust-acoustic time scale, but enough to affect the plasma sheath. We have assumed the current to a dust particle to be balanced throughout the analysis. This makes the grain potential dependent on plasma potential, which is then incorporated into the Poisson equation. The resultant numerical model becomes an initial value problem, which is described by a 1-D integro-differential equation, which is then solved self-consistently by incorporating the change in plasma potential caused by inclusion of the dust potential in the Poisson equation.

  5. An investigation of tendon sheathing filler migration into concrete

    SciTech Connect

    Naus, D.J.; Oland, C.B.

    1998-03-01

    During some of the inspections at nuclear power plants with prestressed concrete containments, it was observed that the containments has experienced leakage of the tendon sheathing filler (i.e., streaks). The objective of this activity was to provide an indication of the extent of tendon sheathing filler leakage into the concrete and its affects on concrete properties. Literature was reviewed and concrete core samples were obtained from the Trojan Nuclear Plant and tested. The literature primarily addressed effects of crude or lubricating oils that are known to cause concrete damage. However, these materials have significantly different characteristics relative to the materials used as tendon sheathing fillers. Examination and testing of the concrete cores indicated that the appearance of tendon sheathing filler on the concrete surface was due to leakage from the conduits and its subsequent migration through cracks that were present. Migration of the tendon sheathing filler was confined to the cracks and there was no perceptible movement into the concrete. Results of compressive strength testing indicated that the concrete quality was consistent in the containment and that the strength had increased over 40% in 25.4 years relative to the average compressive strength at 28-days age.

  6. Structure of the Type VI secretion system contractile sheath

    PubMed Central

    Kudryashev, Mikhail; Wang, Ray Yu-Ruei; Brackmann, Maximilian; Scherer, Sebastian; Maier, Timm; Baker, David; DiMaio, Frank; Stahlberg, Henning; Egelman, Edward H.; Basler, Marek

    2015-01-01

    Summary Bacteria use rapid contraction of a long sheath of the Type VI secretion system (T6SS) to deliver effectors into a target cell. Here we present an atomic resolution structure of a native contracted Vibrio cholerae sheath determined by cryo-electron microscopy. The sheath subunits, composed of tightly interacting proteins VipA and VipB, assemble into a six-start helix. The helix is stabilized by a core domain assembled from four β-strands donated by one VipA and two VipB molecules. The fold of inner and middle layers is conserved between T6SS and phage sheaths. However, the structure of the outer layer is distinct and suggests a mechanism of interaction of the bacterial sheath with an accessory ATPase, ClpV, that facilitates multiple rounds of effector delivery. Our results provide a mechanistic insight into assembly of contractile nanomachines that bacteria and phages use to translocate macromolecules across membranes. PMID:25723169

  7. Sheath folds as a strain gauge in simple shear

    NASA Astrophysics Data System (ADS)

    Adamuszek, Marta; Dabrowski, Marcin

    2017-09-01

    We investigate initiation and evolution of sheath folds developing in multilayer sequences around slip surfaces in simple shear. The slip surface is initially circular and oriented at 135° to the shearing direction. The flow perturbation around the rotating and deforming slip surface initiates the growth of deflections of the layers, which serves as precursors for the sheath structure. The influence of the perturbed flow on the fold growth decreases with strain as the structure is moved away from the slip surface. For γ > 10, the sheath fold evolution is dominated by a passive simple shear. We describe the fold geometry using: 1) interlimb angle (α), 2) apical angle (β), and 3) aspect ratio of the eye-structures in the section normal to the shearing direction at the fold base (Ryz). We show that the fold shapes developing in different interfaces can be characterized by a unique combination of the three parameters depending on strain magnitude. We present three strain gauge diagrams, which can be used to decipher strain from sheath folds based on any combination of two out of three parameters (α, β, Ryz). We approximate the late evolution of the modelled sheath folds by analysing the passive deformation of cone structures in simple shear. We show that Ryz is asymptotically proportional to the square root of strain magnitude.

  8. Sheath formation criterion in magnetized electronegative plasmas with thermal ions

    SciTech Connect

    Hatami, M. M.; Shokri, B.

    2013-03-15

    Taking into account the effect of collisions and positive ion temperatures, the sheath formation criterion is investigated in a weakly magnetized electronegative plasma consisting of electrons, negative and positive ions by using the hydrodynamics equations. It is assumed that the electron and negative ion density distributions are the Boltzmann distribution with two different temperatures. Also, it is assumed that the velocity of positive ions at the sheath edge is not normal to the wall (oblique entrance). Our results show that a sheath region will be formed when the initial velocity of positive ions or the ion Mach number M lies in a specific interval with particular upper and lower limits. Also, it is shown that the presence of the magnetic field affects both of these limits. Moreover, as an practical application, the density distribution of charged particles in the sheath region is studied for an allowable value of M, and it is seen that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when M lies between two above mentioned limits.

  9. Modeling, Theoretical and Observational Studies of the Lunar Photoelectron Sheath

    NASA Astrophysics Data System (ADS)

    Poppe, Andrew Reinhold

    2011-08-01

    The Moon, lacking an atmosphere and a global magnetic field, is directly exposed to both solar ultraviolet radiation and a variety of ambient plasmas. On the lunar dayside, a photoelectron sheath develops and the surface typically charges positively since the photoemission current is at least an order-of-magnitude greater than any ambient current. This sheath dominates the nearsurface plasma environment and controls the charging, levitation and transport of micron-sized dust grains. In this thesis, we first model the lunar near-surface plasma environment via a one-dimensional particle-in-cell code. The sheath potential, electric field and plasma densities are presented over a wide range of plasma parameters. Additionally, the charging and transport of micron- and submicron sized dust grains is modeled via a test-particle approach in an attempt to explain Apolloera observations of lunar dust dynamics. Secondly, we present a comparison of the particle-in-cell results with theoretical, kinetic derivations of the lunar photoelectron sheath. We extend previous theories to include the presence of a kappa-distribution for the solar wind electrons. Finally, we present a comparison of in-situ measurements of the lunar photoelectron sheet in the terrestrial plasma sheet by the Lunar Prospector Electron Reflectometer with particle-in-cell simulations to confirm the presence of non-monotonic sheath potentials above the Moon. Future work in all three sections, (simulation, theory and observation) is presented as a guide for continuing research.

  10. Revisiting the plasma sheath—dust in plasma sheath

    SciTech Connect

    Das, G. C.; Deka, R.; Bora, M. P.

    2016-04-15

    In this work, we have considered the formation of warm plasma sheath in the vicinity of a wall in a plasma with considerable presence of dust particles. As an example, we have used the parameters relevant in case of plasma sheath formed around surfaces of various solid bodies in space, though the results obtained in this work can be applied to any other physical situation such as laboratory plasma. In the ion-acoustic time scale, we neglect the dust dynamics. The dust particles affect the sheath dynamics by affecting the Poisson equation which determines the plasma potential in the sheath region. It is important to note that our calculations are valid only when the amount of dust particles is not sufficient so as to affect the plasma dynamics in the dust-acoustic time scale, but enough to affect the plasma sheath. We have assumed the current to a dust particle to be balanced throughout the analysis. This makes the grain potential dependent on plasma potential, which is then incorporated into the Poisson equation. The resultant numerical model becomes an initial value problem, which is described by a 1-D integro-differential equation, which is then solved self-consistently by incorporating the change in plasma potential caused by inclusion of the dust potential in the Poisson equation.

  11. [The history of the contraceptive sheath].

    PubMed

    Guyotjeannin, C

    1984-06-01

    The condom, effective in preventing both pregnancy and venereal disease, had a limited role until the 19th century, when its use spread through all social strata. The 1st condoms may have been linen sheaths designed to protect against syphilis. A 16th century Neapolitan doctor provided a recipe for an antiseptic preparation to be applied for 4-5 hourrs, but after intercourse had occurred. A physician to Louis XV mentioned the condom in a book published in 1736, and in 1770 the condom was again described without being named. 4 yeears later it was again described and called the condom or English redingote. Later it was mentioned by the Marques de Sade, who alluded to its contraceptive effect. In the early 19th century, condoms made of sheep entrails were mentioned. Descriptions of the preparation of 3 grades of condom, regular, fine, and superfine, were later found. The discovery of the process of vulcanization of rubber in 1839 made possible more solid, marketable, and usable latex condoms. The condom apparently began to be used in the late 17th or early 18th century. Some authors state that it was invented by a Dr. Condom or Conton, a physician or knight in the court of Charls II of England. Othrs suggested that it was named after the city of Condom in Gascony or derived from a foreign word. The antivenereal disease qualities of condoms were described by Casanova and Gustave Flaubert, and other references to them may be found in the literature. Later the contraceptive use of the condom became progressively more common, beginning in the wealthier classes and spreading to the rural and lower classes perhaps by the later 18th century. The diffusion of contraception during the 19th century was cited as the cause of th slow decline in illegitimacy rates starting at the end of the century. The Church condemned the use of condoms for contraception, but the medical profession took a less hostile view due to their health function. At the present time, condoms are widely

  12. Fibroma of tendon sheath in planta.

    PubMed

    Lu, Hui; Chen, Qiang; Shen, Hui; Shen, Xiang-Qian; Wu, Shou-Cheng

    2016-01-01

    Fibroma of tendon sheath in planta is comparatively rare, and its differentiate diagnose, tumour features, treatment and complications were lack of retrospective study in clinics. This was a retrospective study of 13 patients (seven women, six men) operated between July 2001 and May 2013 for FTS in planta. The average age at the time of the procedure was 49.8 ± 8.3 years old (range 31-64). The female-to-male ratio was 9:4. Before the surgery, anteroposterior, lateral and oblique position of foot X-rays were performed in all patients. Ultrasonography (n = 11) and magnetic resonance imaging (n = 11) were performed selectively. The tumor located on the metatarsal par (n = 6), the central part of plantar (n = 4), the lateral part (n = 2) and the medial part (n = 1). Eight patients presented with painless mass (62 % of cases), while five patients presented with pain mass (38 % of cases). No patient had bony erosion. This paper studies the different features of FTS and classifies them into two types-superficial type that tumour grows at planter fascia; deep type that breaks through the planter fascia growing around tendon and joint capsule. Eight and five patients were diagnosed as superficial type and deep type respectively. In all cases, the tumor was excised, pathological results was FTS. The mean follow-up period was 3.2 ± 1.1 years (range 2-7) years. Five patients had neurovascular bundle involvement (38 % of cases). Two patients had a recurrence (15 % of cases), they undergone another operation. Four patients had a pain (31 % of cases), two patients had numbness (15 % of cases), and one patient had pain and numbness (8 % of cases). They recovered after conservative treatment. For the FTS that grows in the plantar, we should select differential diagnosis and the corresponding therapy according to the features of two types, also the prognosis is different. IV.

  13. Characteristics of a Sheath with Secondary Electron Emission in the Double Walls of a Hall Thruster

    NASA Astrophysics Data System (ADS)

    Duan, Ping; Li, Xi; Shen, Hongjuan; Chen, Long; E, Peng

    2012-09-01

    In order to investigate the effects of secondary electrons, which are emitted from the wall, on the performance of a thruster, a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath. The effects of secondary electron emission (SEE) coefficients and trapping coefficients, as well as magnetic field, on the structure of the plasma sheath are investigated. The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness. In addition, magnetic field strength will influence the sheath potential distributions.

  14. Measurement of effective sheath width around cutoff probe in low-pressure plasmas

    SciTech Connect

    Kim, D. W.; Oh, W. Y.; You, S. J. Kim, J. H.; Chang, H. Y.

    2014-05-15

    Previous studies indicated that the measurement results of microwave probes can be improved by applying the adequate sheath width to their measurement models, and consequently the sheath width around the microwave probe tips has become very important information for microwave probe diagnostics. In this paper, we propose a method for measuring the argon plasma sheath width around the cutoff probe tips by applying the circuit model to the cutoff probe phase spectrum. The measured sheath width of the cutoff probe was found to be in good agreement with the floated sheath width calculated from the Child-Langmuir sheath law. The physical reasons for a discrepancy between the two measurements are also discussed.

  15. Anomalous Capacitive Sheath with Deep Radio Frequency Electric Field Penetration

    SciTech Connect

    Igor D. Kaganovich

    2002-01-18

    A novel nonlinear effect of anomalously deep penetration of an external radio-frequency electric field into a plasma is described. A self-consistent kinetic treatment reveals a transition region between the sheath and the plasma. Because of the electron velocity modulation in the sheath, bunches in the energetic electron density are formed in the transition region adjusted to the sheath. The width of the region is of order V(subscript T)/omega, where V(subscript T) is the electron thermal velocity, and w is frequency of the electric field. The presence of the electric field in the transition region results in a cooling of the energetic electrons and an additional heating of the cold electrons in comparison with the case when the transition region is neglected.

  16. Wave rectification in plasma sheaths surrounding electric field antennas

    NASA Technical Reports Server (NTRS)

    Boehm, M. H.; Carlson, C. W.; Mcfadden, J. P.; Clemmons, J. H.; Ergun, R. E.; Mozer, F. S.

    1994-01-01

    Combined measurements of Langmuir or broadband whistler wave intensity and lower-frequency electric field waveforms, all at 10-microsecond time resolution, were made on several recent sounding rockets in the auroral ionosphere. It is found that Langmuir and whistler waves are partically rectified in the plasma sheaths surrounding the payload and the spheres used as antennas. This sheath rectification occurs whenever the high frequency (HF) potential across the sheath becomes of the same order as the electron temperature or higher, for wave frequencies near or above the ion plasma frequency. This rectification can introduce false low-frequency waves into measurements of electric field spectra when strong high-frequency waves are present. Second harmonic signals are also generated, although at much lower levels. The effect occurs in many different plasma conditions, primarily producing false waves at frequencies that are low enough for the antenna coupling to the plasma to be resistive.

  17. Micro-Particles as Electrostatic Probes for Plasma Sheath Diagnostic

    SciTech Connect

    Wolter, Matthias; Haass, Moritz; Ockenga, Taalke; Kersten, Holger; Blazec, Joseph; Basner, Ralf

    2008-09-07

    An interesting aspect in the research of complex (dusty) plasmas is the experimental study of the interaction of micro-particles of different sizes with the surrounding plasma for diagnostic purpose. In the plasma micro-disperse particles are negatively charged and confined in the sheath. The particles are trapped by an equilibrium of gravity, electric field force and ion drag force. From the behavior, local electric fields can be determined, e.g. particles are used as electrostatic probes. In combination with additional measurements of the plasma parameters with Langmuir probes and thermal probes as well as by comparison with an analytical sheath model, the structure of the sheath can be described. In the present work we focus on the behavior of micro-particles of different sizes and several plasma parameters e.g. the gas pressure and the rf-power.

  18. A spine-sheath model for strong-line blazars

    NASA Astrophysics Data System (ADS)

    Sikora, Marek; Rutkowski, Mieszko; Begelman, Mitchell C.

    2016-04-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of `the blazar zone'. We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why γ-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme γ-ray events.

  19. Variability of the Basal Esophageal Sheath in Belondirid Nematodes

    PubMed Central

    Hechler, H. C.

    1969-01-01

    The structure of the basal esophageal sheath was studied in Axonchium amplicolle, A. choristurn, A. crassum, A. gigas, A. micans, A. rotundum, A. serpens, A. solitare, Dorylairnellus aequalis, D. parvulus, D. tenuidens, Oxydirus gangeticus, O. gigus, O. oxycephaloides, and Swangeria bisexualis. In A. gigas the muscle bands comprising the sheath spiral dextrally, but in the other species of Axonchiurn they do not spiral but lie parallel to the esophagus. In O. gigus the spiral is sinistral, whereas in the other two species of Oxydirus it is dextral. The spiral is very slight in Dorylairnellus aequalis, each band passing around only about 180 degrees of the circumference of the esophagus. They completely encircle the esophagus in D. parvulus, and pass around about 3/4 the circumference in D. tenuidens. The definitions of Belondiroidea Thorne, 1964 and of Axonchium Cobb, 1920 are emended to recognize the variability in the structure of the sheath. PMID:19325670

  20. Photovoltaic sheathing element with a flexible connector assembly

    DOEpatents

    Langmaid, Joseph A; Keenihan, James R; Mills, Michael E; Lopez, Leonardo C

    2016-07-12

    The present invention is premised upon an assembly including at least a photovoltaic sheathing element capable of being affixed on a building structure, the sheathing element including at least: a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; at least a first and a second connector assembly disposed on opposing sides of the sheathing element and capable of directly or indirectly electrically connecting the photovoltaic cell assembly to at least two adjoining devices that are affixed to the building structure and wherein at least one of the connector assemblies includes a flexible portion; one or more connector pockets disposed in the body portion the pockets capable of receiving at least a portion of the connector assembly.

  1. Continuum kinetic and multi-fluid simulations of classical sheaths

    NASA Astrophysics Data System (ADS)

    Cagas, P.; Hakim, A.; Juno, J.; Srinivasan, B.

    2017-02-01

    The kinetic study of plasma sheaths is critical, among other things, to understand the deposition of heat on walls, the effect of sputtering, and contamination of the plasma with detrimental impurities. The plasma sheath also provides a boundary condition and can often have a significant global impact on the bulk plasma. In this paper, kinetic studies of classical sheaths are performed with the continuum kinetic code, Gkeyll, which directly solves the Vlasov-Maxwell equations. The code uses a novel version of the finite-element discontinuous Galerkin scheme that conserves energy in the continuous-time limit. The fields are computed using Maxwell equations. Ionization and scattering collisions are included; however, surface effects are neglected. The aim of this work is to introduce the continuum kinetic method and compare its results with those obtained from an already established finite-volume multi-fluid model also implemented in Gkeyll. Novel boundary conditions on the fluids allow the sheath to form without specifying wall fluxes, so the fluids and fields adjust self-consistently at the wall. The work presented here demonstrates that the kinetic and fluid results are in agreement for the momentum flux, showing that in certain regimes, a multi-fluid model can be a useful approximation for simulating the plasma boundary. There are differences in the electrostatic potential between the fluid and kinetic results. Further, the direct solutions of the distribution function presented here highlight the non-Maxwellian distribution of electrons in the sheath, emphasizing the need for a kinetic model. The densities, velocities, and the potential show a good agreement between the kinetic and fluid results. However, kinetic physics is highlighted through higher moments such as parallel and perpendicular temperatures which provide significant differences from the fluid results in which the temperature is assumed to be isotropic. Besides decompression cooling, the heat flux

  2. Sheath dynamics and energetic particle distributions on substrates

    NASA Astrophysics Data System (ADS)

    Lieberman, Michael A.

    2009-10-01

    The energy and angular distributions (EAD's) of energetic particles arriving at a substrate determine crucial plasma processing characteristics; thus knowledge and control of the EAD's are vital for nanoelectronics design and fabrication during scale-down to the ultimate 4--6 nm transistor gate lengths over the next 15 years. We review the history and state-of-the-art of measurements, simulations, and analyses of ion, fast neutral, and ballistic electron EAD's. Ion measurements have been made using electrostatic energy analyzers, cylindrical mirror analyzers, and retarding grid analyzers, often now coupled with quadrupole mass spectrometers to compare different ions in the same discharge. The state-of-the-art for capacitive rf sheaths has advanced greatly since the first observation of a bi-modal ion energy distribution (IED) over 50 years ago. More recently, measurement techniques and models have been developed to determine fast neutral distributions. Monte Carlo, and particle-in-cell simulations with Monte Carlo collisions (PIC-MCC) have been used to study IED's since the late 1980's. Recently, PIC-MCC simulations were used to obtain ballistic electron EAD's. Analytical models of the IED for collisionless rf sheaths have emphasized the role of τi/τrf, the ratio of ion transit time across the sheath to rf period, with separate models for the low and high frequency regimes. Various simplifications and bridging models now exist. For collisional rf sheaths, the important role of λi/s, the ratio of ion-neutral mean free path to sheath width, in modifying the collisionless bi-modal IED was demonstrated in the early 1990's. Surface charging effects on insulating substrates are important for low frequency rf discharges or for pulsed transient sheaths; the latter are found during plasma ion implantation processes. Analytical models of the IED for plasma ion implantation have been extended to insulating surfaces and compared with experimental results.

  3. A time-dependent model of pulse-driven radio frequency capacitively coupled collisional plasma sheath

    NASA Astrophysics Data System (ADS)

    Rahman, M. T.; Hossain, M. Mofazzal

    2017-01-01

    The time-dependent model of ion motion is used to propose an analytical model for dual frequency (DF) capacitively coupled plasma (CCP) sheath driven by a pulsed source and a radio-frequency source. In this model, the sheath is considered to be collisional. In this model, the time dependent terms of ion fluid equations are ignored, but the electric field, ion motion and ion density remain time dependent. Electron profile is assumed to be step-like. Analytical expressions for electron sheath width and sheath potential have been developed. The calculated sheath width and potential are compared with the dual radio frequency driven time dependent models of capacitively coupled plasma sheath. From the temporal evaluation of sheath motion and potential, it has been found that pulse driven sheath has higher sheath potential and sheath width than that of conventional radio frequency driven DF CCP. Moreover, it is also found that ion energy spread can be reduced using pulsed power. From the temporal investigation of sheath motion and potential, it has been found that the duty cycle of the pulse power significantly affects sheath width and sheath potential.

  4. Heat pipe design for sheath insulator reactor test

    SciTech Connect

    Miskolczy, G.; Lee, C.C.M. )

    1991-01-05

    A reactor experiment was designed to test the sheath insulator component of the thermionic fuel element (TFE) of a space power reactor. In this fully instrumented reactor test, two gas-controlled sodium heat pipes will be used to control the temperature of the sheath insulator specimens to which an external voltage will be applied. The heat pipes were designed with the aid of a computer program, which predicted performance. A demonstrator heat pipe was built and electrically tested. The test results agreed with the prediction as modeled by the computer program.

  5. Radiation-induced malignant and atypical peripheral nerve sheath tumors

    SciTech Connect

    Foley, K.M.; Woodruff, J.M.; Ellis, F.T.; Posner, J.B.

    1980-04-01

    The reported peripheral nerve complications of therapeutic irradiation in humans include brachial and lumbar plexus fibrosis and cranial and peripheral nerve atrophy. We have encountered 9 patients with malignant (7) and atypical (2) peripheral nerve tumors occurring in an irradiated site suggesting that such tumors represent another delayed effect of radiation treatment on peripheral nerve. In all instances the radio-theray was within an acceptable radiation dosage, yet 3 patients developed local radiation-induced skin and bony abnormalities. The malignant peripheral nerve sheath tumors developed only in the radiation port. Animal studies support the clinical observation that malignant peripheral nerve sheath tumors can occur as a delayed effect of irradiation.

  6. Malignant Peripheral Nerve Sheath Tumor -A Rare Malignancy in Mandible

    PubMed Central

    Majumdar, Sumit; Kotina, Sreekanth; Uppala, Divya; Kumar, Singam Praveen

    2016-01-01

    Malignant Peripheral Nerve Sheath Tumor (MPNST) is biologically an aggressive tumor that is usually found in the extremities, trunk and infrequently found in the head and neck area particularly in the jaws, arising from the cells allied with nerve sheath. Mandibular MPNST may either arise from a preexisting neurofibroma or develop de novo. Because of the greater variability from case to case in overall appearance both clinically and histologically, a case of MPNST of the mandible in a 25-year-old female patient is reported. The lesion was excised and immunohistological studies (S-100 & Neuron specific enolase) were conducted to confirm the neural origin. PMID:27504425

  7. Modelling Electrostatic Sheath Effects on Swarm Electric Field Instrument Measurements

    NASA Astrophysics Data System (ADS)

    Marchand, R.; Burchill, J. K.; Knudsen, D. J.

    2010-10-01

    The Electric Field Instrument (EFI) was designed to measure ionospheric ion flow velocities, temperatures and distribution functions at the ram face of the European Space Agency’s Swarm spacecraft. These flow velocities, combined with the known orbital velocity of the satellite and local magnetic field, will be used to infer local electric fields from the relation E=- v× B. EFI is among a class of many particle sensors and flow meters mounted on satellites to monitor in situ plasma conditions. The interpretation of the measurements made with EFI and similar sensors relies on a spacecraft sheath model. A common approach, valid in the relatively cold and dense ionospheric plasma, is to assume a potential drop in a thin sheath through which particle deflection and energisation can be calculated analytically. In such models, sheath effects only depend on the spacecraft floating potential, and on the angle of incidence of particles with respect to the normal to the surface. Corrections to measurements are therefore local as they do not depend on the geometry of nearby objects. In an actual plasma, satellites are surrounded by electrostatic sheaths with a finite thickness. As a result, local corrections to particle distribution functions can only be seen as an approximation. A correct interpretation of measured particle fluxes or particle distribution functions must, at least in principle, account for the extent and shape of the sheath in the vicinity of the measuring instrument. This in turn requires a careful analysis of the interaction of the satellite with the surrounding plasma, while accounting for detailed aspects of the geometry, as well as for several physical effects. In this paper, the validity of the thin sheath model is tested by comparing its predictions with detailed PIC (Particle In Cell) calculations of satellite-plasma interaction. Deviations attributed to sheath finite thickness effects are calculated for EFI measurements, with representative plasma

  8. MOLYBDENUM DISILICIDE MATERIALS FOR GLASS MELTING SENSOR SHEATHS

    SciTech Connect

    J. PETROVIC; R. CASTRO; ET AL

    2001-01-01

    Sensors for measuring the properties of molten glass require protective sensor sheaths in order to shield them from the extremely corrosive molten glass environment. MoSi{sub 2} has been shown to possess excellent corrosion resistance in molten glass, making it a candidate material for advanced sensor sheath applications. MoSi{sub 2}-coated Al{sub 2}O{sub 3} tubes, MoSi{sub 2}-Al{sub 2}O{sub 3} laminate composite tubes, and MoSi{sub 2}-Al{sub 2}O{sub 3} functionally graded composite tubes have been produced by plasma spray-forming techniques for such applications.

  9. Dengue Fever with rectus sheath hematoma: a case report.

    PubMed

    Sharma, Anurag; Bhatia, Sonia; Singh, Rajendra Pratap; Malik, Gaurav

    2014-04-01

    Dengue fever, also known as breakbone fever, is an infectious tropical disease caused by the Dengue virus. It is associated with a number of complications, which are well documented. However, Dengue fever associated with rectus sheath hematoma (RSH) is a very rare complication. Only one case report has been published prior supporting the association of Dengue fever with RSH. We report a case of Dengue fever who presented with RSH and was successfully treated conservatively. RSH is also an uncommon cause of acute abdominal pain. It is accumulation of blood in the sheath of the rectus abdominis, secondary to rupture of an epigastric vessel or muscle tear.

  10. Formation of pre-sheath boundary layers in electronegative plasmas

    SciTech Connect

    Vitello, P., LLNL

    1998-05-01

    In electronegative plasmas Coulomb scattering between positive and negative ions can lead to the formation of a pre-sheath boundary layer containing the bulk of the negative ions. The negative ion boundary layer forms when momentum transfer from positive to negative ions dominates the negative ion acceleration from the electric field. This condition is met in Inductively Coupled Plasma reactors that operate at low pressure and high plasma density. Simulations of the GEC reactor for Chlorine and Oxygen chemistries using the INDUCT95 2D model are presented showing the pre-sheath boundary layer structure as a function of applied power and neutral pressure.

  11. Photovoltaic building sheathing element with anti-slide features

    DOEpatents

    Keenihan, James R.; Langmaid, Joseph A.; Lopez, Leonardo C.

    2015-09-08

    The present invention is premised` upon an assembly that includes at least a photovoltaic building sheathing element capable of being affixed on a building structure, the photovoltaic building sheathing element. The element including a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; and at feast a first and a second connector assembly capable of directly or indirectly electrically connecting the photovoltaic cell assembly to one or more adjoining devices; wherein the body portion includes one or more geometric features adapted to engage a vertically adjoining device before installation.

  12. Measurement of effective sheath width around the cutoff probe based on electromagnetic simulation

    SciTech Connect

    Kim, D. W.; Oh, W. Y. E-mail: woh1@kaist.ac.kr; You, S. J. E-mail: woh1@kaist.ac.kr; Kim, J. H.; Chang, H. Y.; Yoon, J.-S.

    2016-05-15

    We inferred the effective sheath width using the cutoff probe and incorporating a full-wave three-dimensional electromagnetic (EM) simulation. The EM simulation reproduced the experimentally obtained plasma-sheath resonance (PSR) on the microwave transmission (S{sub 21}) spectrum well. The PSR frequency has a one-to-one correspondence with the width of the vacuum layer assumed to be the effective sheath in the EM simulation model. The sheath width was estimated by matching the S{sub 21} spectra of the experiment and the EM simulation for different widths of the sheath. We found that the inferred sheath widths quantitatively and qualitatively agree with the sheath width measured by incorporating an equivalent circuit model. These results demonstrate the excellent potential of the cutoff probe for inferring the effective sheath width from its experimental spectrum data.

  13. Malathion aerial spray controls the pine needle -sheath miner

    Treesearch

    Robert E. Stevens

    1966-01-01

    A water emulsion malathion spray, applied by helicopter at the rate of 1 lb. of insecticide in 25 gallons of water, effectively controlled the pine needle-sheath miner (Zelleria haimbachi Busck). Numbers of insects in the sprayed area were reduced by 98.6 percent 24 hours after treatment.

  14. Maize development: cell wall changes in leaves and sheaths

    USDA-ARS?s Scientific Manuscript database

    Developmental changes occur in maize (Zea mays L.) as it transitions from juvenile stages to the mature plant. Changes also occur as newly formed cells mature into adult cells. Maize leaf blades, including the midribs and sheaths, undergo cell wall changes as cells transition to fully mature cell ty...

  15. Rice Sheath Rot: An Emerging Ubiquitous Destructive Disease Complex

    PubMed Central

    Bigirimana, Vincent de P.; Hua, Gia K. H.; Nyamangyoku, Obedi I.; Höfte, Monica

    2015-01-01

    Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium sp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discoloration, chaffiness, and sterility and are all seed-transmitted. Rice sheath rot disease symptoms are found in all rice-growing areas of the world. The disease is now getting momentum and is considered as an important emerging rice production threat. The disease can lead to variable yield losses, which can be as high as 85%. This review aims at improving our understanding of the disease etiology of rice sheath rot and mainly deals with the three most reported rice sheath rot pathogens: S. oryzae, the Fusarium fujikuroi complex, and Pseudomonas fuscovaginae. Causal agents, pathogenicity determinants, interactions among the various pathogens, epidemiology, geographical distribution, and control options will be discussed. PMID:26697031

  16. Studies of RF sheaths and diagnostics on IShTAR

    NASA Astrophysics Data System (ADS)

    Crombé, K.; Devaux, S.; D'Inca, R.; Faudot, E.; Faugel, H.; Fünfgelder, H.; Heuraux, S.; Jacquot, J.; Louche, F.; Moritz, J.; Ochoukov, R.; Tripsky, M.; Van Eester, D.; Wauters, T.; Noterdaeme, J.-M.

    2015-12-01

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  17. Role of the ion plasma frequency in RF sheaths

    NASA Astrophysics Data System (ADS)

    Waelbroeck, F. L.; Hazeltine, R. D.; Xiang, N.

    1999-11-01

    Semiconductor etching relies on rf biasing of the substrate to produce a suitable distribution of energetic ions. The properties of the resulting oscillating sheath depend on two parameters: the ratio of the bias amplitude to the electron temperature, and the ratio of the ion plasma frequency to the rf frequency. In industrial applications, V_rf>> T_e, and nonlinear effects are important. For such large bias the dynamics of the oscillating sheath can be divided into three regimes according to the ratio of the rf frequency to the plasma frequency at the entrance of the sheath and that at the surface of the substrate. Liebermann has given an analytic solution in the high frequency regime. With the increase in plasma density, however, the ion plasma frequency often exceeds the standard rf frequency of 13.56 KHz. We present an analytic solution for the sheath dynamics in the opposite, low-frequency regime. We compare the two regimes, giving particular attention to the distribution of ion energy at the substrate.

  18. Evolutionary sheath structure in magnetized collisionless plasma with electron inertia

    NASA Astrophysics Data System (ADS)

    Gohain, M.; Karmakar, P. K.

    2017-06-01

    A classical hydrodynamic model is methodologically formulated to see the equilibrium properties of a planar plasma sheath in two-component magnetized bounded plasma. It incorporates the weak but finite electron inertia instead of asymptotically inertialess electrons. The effects of the externally applied oblique (relative to the bulk plasma flow) magnetic field are judiciously accented. It is, for the sake of simplicity, assumed that the relevant physical parameters (plasma density, electrostatic potential, and flow velocity) vary only in a direction normal to the confining wall boundary. It is noticed for the first time that the derived Bohm condition for sheath formation is modified conjointly by the electron inertia, magnetic field, and field orientation. It is manifested that the electron inertia in the presence of plasma gyrokinetic effects slightly enhances the ion Mach threshold value (typically, M i0 ≥ 1.139) toward the sheath entrance. This flow super-criticality is in contrast with the heuristic formalism ( M i0 ≥ 1) for the zero-inertia electrons. A numerical illustrative scheme on the parametric sheath features on diverse nontrivial apposite arguments is constructed alongside ameliorative scope.

  19. Study Of Corrosion Of Lead-Sheathed Cables

    NASA Technical Reports Server (NTRS)

    Lee, Rupert U.

    1995-01-01

    Report presents statistical analysis of corrosion failures of lead-sheathed cables that serve as primary communication links at Kennedy Space Center. In study, corrosion-failure data analyzed by use of Weibull distribution in effort to assess effectiveness of cathodic protection and to predict future failures.

  20. On the upper bound in the Bohm sheath criterion

    SciTech Connect

    Kotelnikov, I. A. Skovorodin, D. I.

    2016-02-15

    The question is discussed about the existence of an upper bound in the Bohm sheath criterion, according to which the Debye sheath at the interface between plasma and a negatively charged electrode is stable only if the ion flow velocity in plasma exceeds the ion sound velocity. It is stated that, with an exception of some artificial ionization models, the Bohm sheath criterion is satisfied as an equality at the lower bound and the ion flow velocity is equal to the speed of sound. In the one-dimensional theory, a supersonic flow appears in an unrealistic model of a localized ion source the size of which is less than the Debye length; however, supersonic flows seem to be possible in the two- and three-dimensional cases. In the available numerical codes used to simulate charged particle sources with a plasma emitter, the presence of the upper bound in the Bohm sheath criterion is not supposed; however, the correspondence with experimental data is usually achieved if the ion flow velocity in plasma is close to the ion sound velocity.

  1. Brassica cover cropping for management of sheath blight of rice

    USDA-ARS?s Scientific Manuscript database

    Sheath blight, caused by Rhizoctonia solani, is the most important disease limiting rice production in Texas and other rice-producing states. The fungal pathogen survives between crops as soilborne sclerotia and mycelium in infected plant debris. These sclerotia and colonized plant debris float on t...

  2. The Single Wire Ureteral Access Sheath, Both Safe and Economical

    PubMed Central

    Delto, Joan C.; Sidhu, Ajaydeep; Yanes, Rafael; Bhandari, Akshay

    2016-01-01

    Introduction. Novel disposable products for ureteroscopy are often inherently more expensive than conventional ones. For example, the Cook Flexor© Parallel™ (Flexor) access sheath is designed for ease and efficiency of gaining upper tract access with a solitary wire. We analyze the cost combinations, efficiency, and safety of disposable products utilized for upper tract access, including the Flexor and standard ureteral access sheath. Methods. We performed a retrospective review from January 2014 to October 2014 of patients undergoing URS for nephrolithiasis, who were prestented for various reasons (e.g., infection). Common combinations most utilized at our institution include “Classic,” “Flexor,” and “Standard.” Total costs per technique were calculated. Patient characteristics, operative parameters, and outcomes were compared among the groups. Results. The most commonly used technique involved a standard ureteral sheath and was the most expensive ($294). The second most utilized and least expensive combination involved the Flexor, saving up to $80 per case (27%). All access sheaths were placed successfully and without complications. There were no significant differences in operative time, blood loss, or complications. Conclusions. In prestented patients within this study, the Flexor combination was the most economical. Although the savings appear modest, long-term impact on costs can be substantial. PMID:27974887

  3. Dust-Plasma Sheath in an Oblique Magnetic Field

    SciTech Connect

    Foroutan, G.; Mehdipour, H.

    2008-09-07

    Using numerical simulations of the multi fluid equations the structure of the magnetized sheath near a plasma boundary is studied in the presence of charged dust particles. The dependence of the electron, ion, and dust densities as well as the electrostatic potential, dust charge, and ion normal velocity, on the magnetic field strength and the edge dust number density is investigated.

  4. Synovial sarcoma mimicking benign peripheral nerve sheath tumor.

    PubMed

    Larque, Ana B; Bredella, Miriam A; Nielsen, G Petur; Chebib, Ivan

    2017-07-08

    To assess the radiographic and clinicopathologic features of synovial sarcoma of the nerve that were clinically or radiologically interpreted as benign peripheral nerve sheath tumor. Five patients with synovial sarcoma arising from the peripheral nerve and interpreted clinically and radiologically as peripheral nerve sheath tumors were identified. Clinicopathologic and imaging features were evaluated. There were three females and two males, ranging in age from 28 to 50 (mean 35.8) years. Most patients (4/5) complained of a mass, discomfort or pain. MR images demonstrated a heterogeneous, enhancing, soft tissue mass contiguous with the neurovascular bundle. On histologic examination, most tumors were monophasic synovial sarcoma (4/5). At the time of surgery, all tumors were noted to arise along or within a peripheral nerve. All patients were alive with no evidence of disease with median follow-up of 44 (range 32-237) months. For comparison, approximately 775 benign peripheral nerve sheath tumors of the extremities were identified during the same time period. Primary synovial sarcoma of the nerve can mimic peripheral nerve sheath tumors clinically and on imaging and should be included in the differential diagnosis for tumors arising from peripheral nerves.

  5. Effect of secondary electron emission on the plasma sheath

    SciTech Connect

    Langendorf, S. Walker, M.

    2015-03-15

    In this experiment, plasma sheath potential profiles are measured over boron nitride walls in argon plasma and the effect of secondary electron emission is observed. Results are compared to a kinetic model. Plasmas are generated with a number density of 3 × 10{sup 12} m{sup −3} at a pressure of 10{sup −4} Torr-Ar, with a 1%–16% fraction of energetic primary electrons. The sheath potential profile at the surface of each sample is measured with emissive probes. The electron number densities and temperatures are measured in the bulk plasma with a planar Langmuir probe. The plasma is non-Maxwellian, with isotropic and directed energetic electron populations from 50 to 200 eV and hot and cold Maxwellian populations from 3.6 to 6.4 eV and 0.3 to 1.3 eV, respectively. Plasma Debye lengths range from 4 to 7 mm and the ion-neutral mean free path is 0.8 m. Sheath thicknesses range from 20 to 50 mm, with the smaller thickness occurring near the critical secondary electron emission yield of the wall material. Measured floating potentials are within 16% of model predictions. Measured sheath potential profiles agree with model predictions within 5 V (∼1 T{sub e}), and in four out of six cases deviate less than the measurement uncertainty of 1 V.

  6. Rice Sheath Rot: An Emerging Ubiquitous Destructive Disease Complex.

    PubMed

    Bigirimana, Vincent de P; Hua, Gia K H; Nyamangyoku, Obedi I; Höfte, Monica

    2015-01-01

    Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium sp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discoloration, chaffiness, and sterility and are all seed-transmitted. Rice sheath rot disease symptoms are found in all rice-growing areas of the world. The disease is now getting momentum and is considered as an important emerging rice production threat. The disease can lead to variable yield losses, which can be as high as 85%. This review aims at improving our understanding of the disease etiology of rice sheath rot and mainly deals with the three most reported rice sheath rot pathogens: S. oryzae, the Fusarium fujikuroi complex, and Pseudomonas fuscovaginae. Causal agents, pathogenicity determinants, interactions among the various pathogens, epidemiology, geographical distribution, and control options will be discussed.

  7. Metabolite Diffusion into Bundle Sheath Cells from C4 Plants

    PubMed Central

    Weiner, Hendrik; Burnell, James N.; Woodrow, Ian E.; Heldt, Hans W.; Hatch, Marshall D.

    1988-01-01

    The present studies provide the first measurements of the resistance to diffusive flux of metabolites between mesophyll and bundle sheath cells of C4 plants. Species examined were Panicum miliaceum, Urochloa panicoides, Atriplex spongiosa, and Zea mays. Diffusive flux of metabolites into isolated bundle sheath cells was monitored by following their metabolic transformation. Evidence was obtained that the observed rapid fluxes occurred via functional plasmodesmata. Diffusion constants were determined from the rate of transformation of limiting concentrations of metabolites via cytosolic enzymes with high potential velocities and favorable equilibrium constants. Values on a leaf chlorophyll basis ranged between 1 and 5 micromoles per minute per milligram of chlorophyll per millimolar gradient depending on the molecular weight of the metabolite and the source of bundle sheath cells. Diffusion of metabolites into these cells was unaffected by a wide variety of compounds including respiratory inhibitors, monovalent and divalent cations, and plant hormones, but it was interrupted by treatments inducing cell plasmolysis. The molecular weight exclusion limit for permeation of compounds into bundle sheath cells was in the range of 850 to 900. These cells provide an ideal system for the quantitative study of plasmodesmatal function. PMID:16666390

  8. Malignant peripheral nerve sheath tumour presenting with Horner's syndrome.

    PubMed

    Basuthakur, Sumitra; Sengupta, Amitava; Bandyopadhyay, Ankan; Banerjee, Arpita

    2013-09-01

    A young male presented with clinical and radiological features of right apical lung mass and Horner's syndrome. Subsequently the patient was diagnosed as a case of malignant peripheral nerve sheath tumour (MPNST) at the apex of right lung originating from an intercostal nerve and compressing ipsilateral cervical sympathetic plexus and lower cord of brachial plexus, in a case of neurofibromatosis type 1.

  9. Sheath-blight resistance QTLs and in japonica rice germplasm

    USDA-ARS?s Scientific Manuscript database

    Sheath blight (SB), caused by Rhizoctonia solani, is one of the most serious diseases of cultivated rice (Oryza sativa L.) and genetic resistance is in demand by rice breeders. With the goal of resistance-QTL discovery in U. S. japonica breeding material, a set of 197 F1 doubled-haploid lines (DHLs)...

  10. Separation system with a sheath-flow supported electrochemical detector

    DOEpatents

    Mathies, Richard A [Moraga, CA; Emrich, Charles A [Berkeley, CA; Singhal, Pankaj [Pasadena, CA; Ertl, Peter [Styria, AT

    2008-10-21

    An electrochemical detector including side channels associated with a separation channel of a sample component separation apparatus is provided. The side channels of the detector, in one configuration, provide a sheath-flow for an analyte exiting the separation channel which directs the analyte to the electrically developed electrochemical detector.

  11. High-frequency instability of the sheath-plasma resonance

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.

    1989-01-01

    Coherent high frequency oscillations near the electron plasma frequency (omega approx. less than omega sub p) are generated by electrodes with positive dc bias immersed in a uniform Maxwellian afterglow plasma. The instability occurs at the sheath-plasma resonance and is driven by a negative RF sheath resistance associated with the electron inertia in the diode-like electron-rich sheath. With increasing dc bias, i.e., electron transit time, the instability exhibits a hard threshold, downward frequency pulling, line broadening and copious harmonics. The fundamental instability is a bounded oscillation due to wave evanescence, but the harmonics are radiated as electromagnetic waves from the electrodes acting like antennas. Wavelength and polarization measurements confirm the emission process. Electromagnetic waves are excited by electrodes of various geometries (planes, cylinders, spheres) which excludes other radiation mechanisms such as orbitrons or beam-plasma instabilities. The line broadening mechanism was identified as a frequency modulation via the electron transit time by dynamic ions. Ion oscillations at the sheath edge give rise to burst-like RF emissions. These laboratory observations of a new instability are important for antennas in space plasmas, generation of coherent beams with diodes, and plasma diagnostics.

  12. On radiative acceleration in spine-sheath structured blazar jets

    NASA Astrophysics Data System (ADS)

    Chhotray, A.; Nappo, F.; Ghisellini, G.; Salafia, O. S.; Tavecchio, F.; Lazzati, D.

    2017-04-01

    It has been proposed that blazar jets are structured, with a fast spine surrounded by a slower sheath or layer. This structured jet model explains some properties of their emission and morphology. Because of their relative motion, the radiation produced by one component is seen amplified by the other, thus enhancing the inverse Compton emission of both. Radiation is emitted anisotropically in the comoving frames and causes the emitting plasma to recoil. As seen in the observer frame, this corresponds to a deceleration of the fastest component (the spine) and an acceleration of the slower one (the layer). While the deceleration of the spine has already been investigated, here we study for the first time the acceleration of the sheath and find self-consistent velocity profile solutions for both the spine and the sheath while accounting for radiative cooling. We find that the sheath can be accelerated to the velocities required by the observations if its leptons remain energetic in the acceleration region, assumed to be of the order of ˜100 Schwarzschild radii, demanding continuous injection of energetic particles in that region.

  13. Rectus sheath hematoma: a complication of laparoscopic cholecystectomy.

    PubMed

    Neufeld, D; Jessel, J; Freund, U

    1992-12-01

    We describe a complication in laparoscopic cholecystectomy. The routine introduction of a midclavicular secondary trocar resulted in a large hematoma of the rectus sheath. The patient developed atelectasis and pneumonia and required extended hospitalization. This previously described complication is detailed with recommendations to prevent its occurrence.

  14. Permeability of the Suberized Mestome Sheath in Winter Rye 1

    PubMed Central

    Peterson, Carol A.; Griffith, Marilyn; Huner, Norman P. A.

    1985-01-01

    Mestome sheath cells of winter rye (Secale cereale L. cv Puma) deposit suberized lamellae in their secondary cell walls. Histochemical tests including acid digestion and staining with Sudan IV and Chelidonium majus root extract were used to detect the presence of suberin in the primary cell wall. There was no evidence of a Casparian band between adjacent mestome sheath cells. Fluorescent dye techniques were used to trace solute movement through the rye leaf apoplast. Calcofluor white M2R, a fluorescent dye which binds to cell walls as it moves apoplastically, proved to be too limited in its mobility in leaves to test mestome sheath permeability. Trisodium 3-hydroxy-5,8,10 pyrene trisulfonate, a fluorescent dye which is mobile in the apoplast, moved easily up the vascular bundles in the transpiration stream, and diffused outward from the veins to the epidermal cell walls within minutes of reaching a particular level in the leaf. We conclude that the suberized mestome sheath of rye leaves is freely permeable to solutes moving apoplastically through radial primary cell walls. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:16663999

  15. Internal pressure effects in the AIRCO-LCT conductor sheath

    SciTech Connect

    Luton, J.N.; Clinard, J.A.; Lue, J.W.; Gray, W.H.; Summers, L.T.; Kershaw, R.

    1985-01-01

    The large Nb/sub 3/Sn superconducting test coil produced by Westinghouse Electric Corporation for the international Large Coil Task (LCT) utilizes a conductor composed of cabled multifilamentary strands immersed in flowing supercritical helium contained by a square structural sheath made of the high-strength stainless alloy JBX-75. Peak pressures of a few hundred atmospheres are predicted to occur during quench, and measurement of these pressures seems feasible only through penetrations of the sheath wall. Fully processed short lengths of conductor were taken from production ends, fitted with pressure taps and strain gauges, and pressurized with helium gas. Failure, at 1000 atm at liquid nitrogen temperature, was by a catastrophic splitting of the sheath at a corner. Strain measurements and burst pressure agreed with elastic-plastic finite element stress calculations made for the sheath alone. Neither the production seam weld nor the pressure tap penetrations or their fillet welds contributed to the failure, although the finite element calculations show that these areas were also highly stressed, and examination of the failed sample showed that the finite welds were of poor quality. Failure was by tensile overload, with no evidence of fatigue.

  16. Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

    NASA Astrophysics Data System (ADS)

    Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

    2015-12-01

    Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

  17. Elongation pattern and fine structure of the sheaths formed by Thiothrix nivea and Thiothrix fructosivorans.

    PubMed

    Kawasaki, Yuta; Endo, Tomoyuki; Fujiwara, Atsuo; Kondo, Keiko; Katahira, Masato; Nittami, Tadashi; Sato, Michio; Takeda, Minoru

    2017-02-01

    Thiothrix strains are filamentous sulfur-oxidizing bacteria common in activated sludge. Some of the members, including Thiothrix nivea and T. fructosivorans, are known to form a microtubular sheath that covers a line of cells. The sheaths are assemblages of [→4)-β-d-GlcN-(1→4)-β-d-Glc-(1→]n modified with unusual deoxy sugars. In an attempt to elucidate the sheath-forming mechanism, the patterns of sheath formation and cell proliferation were determined in this study. Prior to analysis, both sheaths were confirmed to be highly de-N-acetylated. Sheaths in viable filaments were N-biotinylated followed by cultivation and then fluorescently immunostained. Epifluorescence microscopy of the filaments revealed ubiquitous elongation of the sheaths. For visualization of the cell proliferation pattern, the cell membrane was fluorescently stained. The epifluorescence images demonstrated that cell proliferation also proceeds ubiquitously, suggesting that sheath elongation proceeds surrounding an elongating cell. In addition, the fine structure of the Thiothrix filaments was analyzed by transmission electron microscopy employing a freeze-substitution technique. The micrographs of freeze-substituted filaments showed that the sheaths were thin and single layered. In contrast, the sheaths in chemically fixed filaments appeared thick and multilayered. Treatment with glutaraldehyde probably caused deformation of the sheaths. Supporting this possibility, the sheaths were found to be deformed or solubilized by N-acetylation.

  18. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Armored and metallic sheathed cable. 111.05-7 Section 111.05-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the...

  19. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Armored and metallic sheathed cable. 111.05-7 Section 111.05-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the...

  20. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Armored and metallic sheathed cable. 111.05-7 Section 111.05-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the...

  1. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Armored and metallic sheathed cable. 111.05-7 Section 111.05-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the...

  2. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Armored and metallic sheathed cable. 111.05-7 Section 111.05-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the...

  3. Do counts of salivary sheath flanges predict food consumption in herbivorous stink bugs [Hemiptera: Pentatomidae]?

    USDA-ARS?s Scientific Manuscript database

    For Pentatomid stink bug agricultural pests, the number of salivary sheaths and sheath flanges—the portion of the sheath visible on the exterior surface of a food item—are good predictors of the loss of crop yield or quality from stink bug feeding. As the often assumed relationship between salivary ...

  4. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified...

  5. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified...

  6. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified...

  7. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified...

  8. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified...

  9. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Grounding metallic sheaths, armors, and... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout and...

  10. 30 CFR 77.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Grounding metallic sheaths, armors, and... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Grounding § 77.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. Metallic sheaths, armors, and conduits enclosing power...

  11. 30 CFR 77.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Grounding metallic sheaths, armors, and... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Grounding § 77.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. Metallic sheaths, armors, and conduits enclosing power...

  12. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Grounding metallic sheaths, armors, and... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout and...

  13. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Grounding metallic sheaths, armors, and... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout and...

  14. 30 CFR 77.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Grounding metallic sheaths, armors, and... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Grounding § 77.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. Metallic sheaths, armors, and conduits enclosing power...

  15. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Grounding metallic sheaths, armors, and... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout and...

  16. 30 CFR 77.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Grounding metallic sheaths, armors, and... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Grounding § 77.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. Metallic sheaths, armors, and conduits enclosing power...

  17. Evolution of Piled Up Compressions in Modeled CME Sheaths and the Resulting Sheath Structures

    NASA Astrophysics Data System (ADS)

    Das, I.; Opher, M.; Evans, R. M.; Gombosi, T. I.

    2010-12-01

    We study Coronal Mass Ejection (CME) driven shocks and the resulting post shock structures in the lower corona (~ 2-7 Rsun). Two CMEs are erupted by modified Titov-Demoulin (TD) and Gibson-Low (GL) type flux ropes with Space Weather Modeling Framework. We observe a substantial pile up of density compression and a narrow region of plasma depletion layer (PDL) in the simulations. As the CME/flux rope moves and expands in solar wind medium, it pushes the magnetized material laying ahead of it. Hence, the magnetic field lines draping around the CME front are compressed in the sheath just ahead of the CME. These compressed field lines squeeze out the plasma sideways forming PDL in the region. Solar plasma being pushed and displaced from behind, forms a strong piled up compression (PUC) of density downstream of the PDL. Both CMEs have comparable propagation speeds while GL has larger expansion speed than TD due to its higher initial magnetic pressure. We argue that high CME expansion speed along with high solar wind density in the region are responsible for the large PUC found in the lower corona. In case of GL the PUC is much wider although the density compression ratio for both the cases are comparable. Although these simulations artificially initiate out-of-equilibrium CMEs and drive them in an artificial solar wind solution, we predict that PUCs, in general, will be large in the lower corona. This should affect the ion profiles of the accelerated solar energetic particles.

  18. The 10 sheath-accelerated electrons and ions. [atmospheric models of plasma sheaths and ionospheric electron density

    NASA Technical Reports Server (NTRS)

    Shawhan, S. D.

    1975-01-01

    A model is presented that suggests that plasma sheaths form between the ionospheric plasma moving with Io and the ambient plasma corotating with Jupiter. Potentials across these sheaths could be as high as 580 kV which is the motional emf across Io's ionosphere. Electrons and ions can be accelerated across these sheaths. The sheaths may exist at the top of the Io ionosphere with characteristic thicknesses of 1/4 kilometers. The model is consistent with the Pioneer observations of 0.15 MeV electrons at the inner edge of Io's L-shell and the enhanced number density of low-energy protons at the outer edge. Ion sputtering of the Io surface is discussed and may explain the presence of atomic hydrogen and sodium in the vicinity of Io. Also these accelerated particles may be important to the formation of the Io ionosphere. High electron flux which may lead to decametric radio emissions, Jovian atmospheric heating and optical and X-ray emissions is also discussed.

  19. Hydrophilic coating aids radial sheath withdrawal and reduces patient discomfort following transradial coronary intervention: a randomized double-blind comparison of coated and uncoated sheaths.

    PubMed

    Kiemeneij, Ferdinand; Fraser, Douglas; Slagboom, Ton; Laarman, GertJan; van der Wieken, Ron

    2003-06-01

    Radial artery spasm may cause severe discomfort during radial artery sheath removal. A hydrophilic-coated sheath may reduce the force required to remove a radial sheath. This force may be quantified using an automatic pullback device (APD). The objective of this study was to assess if a hydrophilic coating reduces the required force and discomfort associated with removal of a radial sheath following transradial coronary intervention. Ninety patients undergoing percutaneous coronary intervention via the radial artery were randomly assigned to two groups receiving either coated or uncoated introducer sheaths. Radifocus Introducer II (Terumo) 25 cm, 6 Fr radial sheaths and sheaths that were identical apart from the presence of the coating were used in all patients. The APD was used for sheath removal at the end of the procedure. Three patients (7%) in the coated group experienced discomfort during automatic sheath removal, compared to 12 patients (27%) in the uncoated group (P = 0.02). The maximum pullback force (MPF) was significantly lower in the coated compared to the uncoated group (0.24 +/- 0.31 vs. 0.44 +/- 0.33 kg; P = 0.003). Similarly, the mean pullback force was significantly lower in the coated group (0.14 +/- 0.23 vs. 0.32 +/- 0.24 kg; P < 0.001). Only one patient (2%) in each group had an MPF greater than 1.0 kg together with clinical evidence of radial artery spasm. Removal of the coated Terumo Radifocus sheath requires less force than an identical uncoated sheath. The coated sheath was also associated with less discomfort for the patient.

  20. Radio-frequency sheath voltages and slow wave electric field spatial structure

    NASA Astrophysics Data System (ADS)

    Colas, Laurent; Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan

    2015-12-01

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the RF parallel electric field emitted by Ion Cyclotron (IC) wave launchers, using a simple model of Slow Wave (SW) evanescence coupled with Direct Current (DC) plasma biasing via sheath boundary conditions in a plasma-filled 2-dimensional (parallel, radial) rectangle. Within a "wide sheaths" asymptotic regime, valid for large-amplitude near RF fields, our model becomes partly linear: the sheath oscillating voltage at open field line boundaries is a linear combination of elementary contributions by every source point of the radiated RF field map. These individual contributions are all the more intense as the SW emission point is toroidally nearer to the sheath walls. A limit formula is given for a source infinitely close to the sheaths. The decay of sheath RF voltages with the sheath/source parallel distance is quantified as a function of two characteristic SW evanescence lengths. Decay lengths are smaller than antenna parallel extensions. The sheath RF voltages at an IC antenna side limiter are therefore mainly sensitive to SW emission near this limiter, as recent observations suggest. Toroidal proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel anti-symmetry of the radiated field map. They could also justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  1. In vivo engineering of a functional tendon sheath in a hen model.

    PubMed

    Xu, Liang; Cao, Dejun; Liu, Wei; Zhou, Guangdong; Zhang, Wen Jie; Cao, Yilin

    2010-05-01

    Repair of injured tendon sheath remains a major challenge and this study explored the possibility of in vivo reconstruction of a tendon sheath with tendon sheath derived cells and polyglycolic acid (PGA) fibers in a Leghorn hen model. Total 55 Leghorn hens with a 1cm tendon sheath defect created in the left middle toe of each animal were randomly assigned into: (1) experimental group (n=19) that received a cell-PGA construct; (2) scaffold control group (n=18) that received a cell-free PGA scaffold; (3) blank control group (n=18) with the defect untreated. Tendon sheath cells were isolated, in vitro expanded, and seeded onto PGA scaffolds. After in vitro culture for 7 days, the constructs were in vivo implanted to repair the sheath defects. Alcian blue staining confirmed the ability of cultured cells to produce specific matrices containing acidic carboxyl mucopolysaccharide (mainly hyaluronic acid). In addition, the engineered sheath formed a relatively mature structure at 12 weeks post-surgery, which was similar to that of native counterpart, including a smooth inner surface, a well-developed sheath histological structure with a clear space between the tendon and the engineered sheath. More importantly, Work of Flexion assay revealed that the tendons needed less power consumption to glide inside the engineered sheath when compared to the tendons which were surrounded by scar-repaired tissues, indicating that the engineered sheaths had gained the function to a certain extent of preventing tendon adhesion. Taken together, these results suggest that tendon sheaths that are functionally and structurally similar to native sheaths are possible to be engineered in vivo using tendon sheath cells and PGA scaffolds. Copyright 2010 Elsevier Ltd. All rights reserved.

  2. Co-electrospinning fabrication and photocatalytic performance of TiO{sub 2}/SiO{sub 2} core/sheath nanofibers with tunable sheath thickness

    SciTech Connect

    Cao, Houbao Du, Pingfan; Song, Lixin; Xiong, Jie Yang, Junjie; Xing, Tonghai; Liu, Xin; Wu, Rongrong; Wang, Minchao; Shao, Xiaoli

    2013-11-15

    Graphical abstract: - Highlights: • The core–sheath TiO{sub 2}/SiO{sub 2} nanofibers were fabricated by co-electrospinning technique. • The catalytic property of nanofibers with different sheath thickness was studied. • The potential methods of improving catalytic efficiency are suggested. - Abstract: In this paper, core/sheath TiO{sub 2}/SiO{sub 2} nanofibers with tunable sheath thickness were directly fabricated via a facile co-electrospinning technique with subsequent calcination at 500 °C. The morphologies and structures of core/sheath TiO{sub 2}/SiO{sub 2} nanofibers were characterized by TGA, FESEM, TEM, FTIR, XPS and BET. It was found that the 1D core/sheath nanofibers are made up of anatase–rutile TiO{sub 2} core and amorphous SiO{sub 2} sheath. The influences of SiO{sub 2} sheath and its thickness on the photoreactivity were evaluated by observing photo-degradation of methylene blue aqueous solution under the irradiation of UV light. Compared with pure TiO{sub 2} nanofibers, the core/sheath TiO{sub 2}/SiO{sub 2} nanofibers performed a better catalytic performance. That was attributed to not only efficient separation of hole–electron pairs resulting from the formation of heterojunction but also larger surface area and surface silanol group which will be useful to provide higher capacity for oxygen adsorption to generate more hydroxyl radicals. And the optimized core/sheath TiO{sub 2}/SiO{sub 2} nanofibers with a sheath thickness of 37 nm exhibited the best photocatalytic performance.

  3. Moisture Durability with Vapor-Permeable Insulating Sheathing

    SciTech Connect

    Lepage, R.; Lstiburek, J.

    2013-09-01

    Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However,uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and theprocedures utilized to analyse the problems.

  4. Moisture Durability with Vapor-Permeable Insulating Sheathing

    SciTech Connect

    Lepage, R.; Lstiburek, J.

    2013-09-01

    Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However, uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and the procedures utilized to analyse the problems.

  5. Recent sheath physics studies on DIII-D

    NASA Astrophysics Data System (ADS)

    Watkins, J. G.; Labombard, B.; Stangeby, P. C.; Lasnier, C. J.; McLean, A. G.; Nygren, R. E.; Boedo, J. A.; Leonard, A. W.; Rudakov, D. L.

    2015-08-01

    A study to examine some current issues in the physics of the plasma sheath has been recently carried out in DIII-D low power Ohmic plasmas using both flush and domed Langmuir probes, divertor Thomson scattering (DTS), an infrared camera (IRTV), and a new calorimeter triple probe assembly mounted on the Divertor Materials Evaluation System (DIMES). The sheath power transmission factor was found to be consistent with the theoretically predicted value of 7 (±2) for low power plasmas. Using this factor, the three heat flux profiles derived from the LP, DTS, and calorimeter diagnostic measurements agree. Comparison of flush and domed Langmuir probes and divertor Thomson scattering indicates that proper interpretation of flush probe data to get target plate density and temperature is feasible and could potentially yield accurate measurements of target plate conditions where the probes are located.

  6. Leptomeningeal metastasis of an intradural malignant peripheral nerve sheath tumor.

    PubMed

    Stark, Andreas M; Mehdorn, H Maximilian

    2013-08-01

    Malignant peripheral nerve sheath tumors (MPNST) are defined as any malignant tumor arising from or differentiating towards the peripheral nerve sheath. Intradural MPNST metastases are very rare. We report, to our knowledge, the first case of leptomeningeal metastasis of a MPNST to the spine and intracranial space. A 56-year-old woman with primary intradural MPNST of the S1 nerve root developed leptomeningeal metastases as well as brain metastases 19 months after diagnosis. The patient had a history of non-Hodgkins lymphoma for which she had received irradiation to the spine 15 years prior to this presentation. She had no stigmata of neurofibromatosis type 1. Patients with MPNST may also develop leptomeningeal metastases as demonstrated in this patient with intradural post-radiation MPNST.

  7. The sheath structure around a negatively charged rocket payload

    NASA Technical Reports Server (NTRS)

    Neubert, T.; Gilchrist, B. E.; Banks, P. M.; Mandell, M. J.; Sasaki, S.

    1990-01-01

    The sheath structure around a rocket payload charged up to 460 V negative relative to the ambient ionospheric plasma is investigated experimentally and by computer simulations. The experimental results come from the Charge 2 sounding rocket experiment in which the payload was split into two separate sections (mother and daughter) connected with a conducting, insulated tether. In one of the experimental modes, the voltage between the payloads was increased linearly from 0 to 460 V in 2.5 s. A floating probe array was mounted on the mother with probes located 25, 50, 75, and 100 cm from the rocket surface. The internal impedance of the array was smaller than the probe/plasma impedance, which influenced the potential measurements. The measurements contain signatures, resulting from the outward expansion of the ion sheath with increasing negative mother potential. This conclusion is substantiated by computer simulations of space charge limited flow.

  8. Fluid and kinetic models of negative ion sheaths

    SciTech Connect

    Cavenago, M.

    2011-09-26

    Due to the presence of a large transverse magnetic field (B{sub x} and B{sub y} where z is the extraction axis), the extraction of electrons from a negative ion source is likely to happen with a large angle with respect to z axis. The negative ion and electron sheaths are here studied both with kinetic and with fluid models. First, Vlasov-Poisson models are reduced to one dimensional integrodifferential equations, discussing also trapped orbits. The integrodifferential equations for electron transport are analytically solved for a variety of extraction potentials (in 1D). Collision frequency dependency from electron flow speed and temperature is discussed. Then both ion and electron space charge and fluid motion are solved, using electron densities expression consistent with kinetic model. Results for the sheath charge profile and extraction field as a function of B{sub x} are shown.

  9. Role of magnetic field tangency points in ICRF sheath interactions

    SciTech Connect

    Myra, J. R.; D'Ippolito, D. A.; Kohno, H.

    2014-02-12

    ICRF waves can sometimes interact with plasma-facing surfaces in tokamak fusion experiments causing degradation of core heating efficiency, impurity injection and even component damage. While presently available low dimensionality rf sheath models are useful in understanding many features of these interactions, more quantitative modeling will require attention to realistic geometrical details of the boundary plasma and surfaces. In this paper, we explore the situation in which there exists a tangency point of the background magnetic field with a surface. We find that the rf interactions are strongly influenced by the generation and propagation of sheath-plasma waves (SPW) along the surface. It is found that these waves preferentially propagate towards, and accumulate at, a convex tangency point. An analytical theory of SPW propagation is developed to understand these features.

  10. Photovoltaic sheathing element with one or more tabs

    DOEpatents

    Keenihan, James R; Langmaid, Joseph A; Lopez, Leonardo C.

    2017-02-07

    The present invention is premised upon an assembly that includes at least a photovoltaic sheathing element capable of being affixed on a building structure. The shingle including at least a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly. Wherein the body portion includes one or more top peripheral tabs each capable of fitting under one or more vertically adjoining devices.

  11. Therapy of Experimental Nerve Sheath Tumors Using Oncolytic Viruses

    DTIC Science & Technology

    2005-06-01

    SUPPLEMENTARY NOTES 14. ABSTRACT Abstract follows. 15. SUBJECT TERMS Oncolytic HSV, angiogenesis, MPNST , mouse model 16. SECURITY CLASSIFICATION OF: 17...reliable tumor models for malignant peripheral nerve sheath tumors ( MPNST ). Several existing and novel oncolytic HSV vectors will then be tested on these...from G47A increases cytotoxicity in vitro to human endothelial cells and murine Nfl" MPNST cell lines. Inhibition of MPNST M2 tumor growth in vivo was

  12. Studies of RF sheaths and diagnostics on IShTAR

    SciTech Connect

    Crombé, K.; D’Inca, R.; Faugel, H.; Fünfgelder, H.; Jacquot, J.; Ochoukov, R.; Louche, F.; Tripsky, M.; Van Eester, D.; Wauters, T.

    2015-12-10

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  13. Electron collection by multiple objects within a single sheath

    NASA Technical Reports Server (NTRS)

    Davis, V. A.; Mandell, M. J.; Katz, I.

    1988-01-01

    NASCAP/LEO, a computer program for the three-dimensional simulation of high-voltage surfaces with plasma, has been developed as a tool in the design of reliable, high-power spacecraft. NASCAP/LEO computes the potentials using analytic formulations for space charge, and only uses particle tracking to compute the current to the surfaces. Carruth's (1987) experimental results agree with the NASCAP/LEO simulations for the cases of both individual and overlapping sheaths.

  14. Plasma-sheath effects on the Debye screening problem

    SciTech Connect

    Sarmah, D.; Tessarotto, M.; Salimullah, M.

    2006-03-15

    The classical Debye-Hueckel screening effect of the electrostatic field generated by isolated charged particles immersed in a plasma is reviewed. The validity of the underlying mathematical model, and particularly of the weak-field approximation, is analyzed. It is shown that the presence of the plasma sheath around test particles and the resulting effect of charge screening are essential for the description of plasmas that are strongly coupled.

  15. INTERIOR OF HOG BARN SHOWING MILKING STANCHIONS AND DIAGONAL SHEATHING, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR OF HOG BARN SHOWING MILKING STANCHIONS AND DIAGONAL SHEATHING, LOOKING EAST. (In the 1940s the hog barn was converted to a calf barn to service the growing dairy. After a fire on the property took the Engle’s main barn in 1954, the building was converted into a milking parlor.) - Engle Farm, Barn, 89 South Ebey Road, Coupeville, Island County, WA

  16. Nonextensivity effect on radio-wave transmission in plasma sheath

    NASA Astrophysics Data System (ADS)

    Mousavi, A.; Esfandiari-Kalejahi, A.; Akbari-Moghanjoughi, M.

    2016-04-01

    In this paper, new theoretical findings on the application of magnetic field in effective transmission of electromagnetic (EM) waves through a plasma sheath around a hypersonic vehicle are reported. The results are obtained by assuming the plasma sheath to consist of nonextensive electrons and thermal ions. The expressions for the electric field and effective collision frequency are derived analytically in the framework of nonextensive statistics. Examination of the reflection, transmission, and absorption coefficients regarding the strength of the ambient magnetic field shows the significance of q-nonextensive parameter effect on these entities. For small values of the magnetic field, the transmission coefficient increases to unity only in the range of - 1 < q < 1 . It is also found that the EM wave transmission through the nonextensive plasma sheath can take place using lower magnetic field strengths in the presence of superthermal electrons compared with that of Maxwellian ones. It is observed that superthermal electrons, with nonextensive parameter, q < 1, play a dominant role in overcoming the radio blackout for hypersonic flights.

  17. Ion flow and sheath structure near positively biased electrodes

    NASA Astrophysics Data System (ADS)

    Hood, R.; Scheiner, B.; Baalrud, S. D.; Hopkins, M. M.; Barnat, E. V.; Yee, B. T.; Merlino, R. L.; Skiff, F.

    2016-11-01

    What effect does a dielectric material surrounding a small positively biased electrode have on the ion flow and sheath structure near the electrode? Measurements of the ion velocity distribution function and plasma potential near positively biased electrodes were made using laser-induced fluorescence and an emissive probe. The results were compared with 2D particle-in-cell simulations. Both measurements and simulations showed that when the positive electrode was surrounded by the dielectric material, ions were accelerated toward the electrode to approximately 0.5 times the ion sound speed before being deflected radially by the electron sheath potential barrier of the electrode. The axial potential profile in this case contained a virtual cathode. In comparison, when the dielectric material was removed from around the electrode, both the ion flow and virtual cathode depth near the electrode were dramatically reduced. These measurements suggest that the ion presheath from the dielectric material surrounding the electrode may enclose the electron sheath of the electrode, resulting in a virtual cathode that substantially influences the ion flow profile in the region.

  18. Investigation of plasma-sheath resonances in low pressure discharges

    NASA Astrophysics Data System (ADS)

    Naggary, Schabnam; Kemaneci, Efe; Brinkmann, Ralf Peter; Megahed, Mustafa

    2016-09-01

    Plasma sheath resonances (PSR) arise from a periodic exchange between the kinetic electron energy in the plasma bulk and the electric field energy in the sheath and can easily be excited by the sheath-generated harmonics of the applied RF. In this contribution, we employ a series of models to obtain a well-defined description of these phenomena. In the first part, we use a global model to study the influence of the nonlinear charge-voltage characteristics on the electron dynamics. However, the global model is restricted to the assumption of spatially constant potential at each driven and grounded electrode and thus delivers only the fundamental mode of the current. In order to remedy the deficiency, we introduce a spatially resolved model for arbitrary reactor geometries with no assumptions on the homogeneity of the plasma. An exact evaluation of the analytical solution is realized on the assumption of a cylinderical plasma reactor geometry with uniform conductance. Furthermore, the spatially resolved model is capable of being utilized for a more realistic CCP reactor geometry and non homogeneous plasma provided the conductance distribution is known. For this purpose, we use the CFD-ACE+ tool. The results show that the proposed multi-mode model provides a significant improvement. The authors gratefully acknowledge the financial support by the ESI Group and the SFB- TR 87.

  19. Unified Model of the rf Plasma Sheath, Part II

    NASA Astrophysics Data System (ADS)

    Riley, Merle

    1996-10-01

    By developing an approximation to the first integral of the Poisson equation, one can obtain solutions for the current-voltage characteristics of an rf plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current. (M.E.Riley, 1995 GEC, abstract QA5, published in Bull. Am. Phys. Soc., 40, 1587 (1995).) The theory has been shown to adequately reproduce current-voltage characteristics of two extreme cases (M.A. Lieberman, IEEE Trans. Plasma Sci. 16, 638 (1988). A. Metze, D.W. Ernie, and H.J.Oskam, J.Appl.Phys., 60, 3081 (1986).) of ion response. In this work I show the effect of different conventions for connecting the sheath model to the bulk plasma. Modifications of the Mach number and a finite electric field at the Bohm point are natural choices. The differences are examined for a sheath in a high density Ar plasma and are found to be insignificant. A theoretical argument favors the electric field modification. *Work performed at Sandia National Labs and supported by US DoE under contract DE-AC04-94AL85000.

  20. Structure of the bipolar plasma sheath generated by SPEAR I

    SciTech Connect

    Katz, I.; Jongeward, G.A.; Davis, V.A.; Mandell, M.J.; Kuharski, R.A.; Lilley, J.R. Jr. ); Raitt, W.J. ); Cooke, D.L. ); Torbert, R.B.; Larson, G.; Rau, D. )

    1989-02-01

    The Space Power Experiment Aboard Rockets I (SPEAR I) biased two 10-cm radius spheres as high as 46,000 V positive with respect to an aluminum rocket body. The experiment measured the steady state current to the spheres and the floating potential of the rocket body. Three-dimensional calculations performed using NASCAP/LEO and POLAR 2.0 show that both ion-collecting and electron-collecting sheaths were formed. The rocket body potential with respect to the ionospheric plasma adjusted to achieve a balance between the electron current collected by the spheres and the secondary electron-enhanced ion current to the rocket body. This current balance was obtained with a large ion-collecting sheath that enveloped most of the electron-collecting sheath and reduced the area for collection of ionospheric electrons. The calculated current is in agreement with the flight measurement of a steady state current of less than 1/10 A. The calculations show that the rocket body was driven thousands of volts negative with respect to the ionospheric plasma. The calculated rocket potential is within the uncertainty of that inferred from ion spectrometer data. The current flowed through the space plasma. There was almost no direct charge transport between the spheres and the rocket body.

  1. Differential expression of angiogenic factors in peripheral nerve sheath tumors.

    PubMed

    Wasa, Junji; Nishida, Yoshihiro; Suzuki, Yoshitaka; Tsukushi, Satoshi; Shido, Yoji; Hosono, Kozo; Shimoyama, Yoshie; Nakamura, Shigeo; Ishiguro, Naoki

    2008-01-01

    It is difficult to differentiate some malignant peripheral nerve sheath tumors (MPNST) from benign peripheral nerve sheath tumors (BPNST) histologically, and to predict the clinical outcome of patients with MPNST. In this study, the expression of VEGF and MVD were evaluated immunohistochemically in 22 cases of MPNST, 14 of neurofibroma and 19 of schwannoma and correlation of the staining grade of VEGF or MVD and the various clinical factors were analyzed, and statistically evaluated. Levels of VEGF mRNA expression were also determined with real-time RT-PCR. Statistically higher positive staining for VEGF was observed in MPNST compared to neurofibroma (P=0.004) and schwannoma (P<0.001). Even low grade MPNST showed higher VEGF positive staining than neurofibroma. Moreover, high VEGF expression statistically correlated with the poor prognosis of the patients with MPNST (P=0.015). Although MVD in MPNST was significantly higher than that in neurofibroma (P=0.038) and schwannoma (P<0.001), MVD could not predict the prognosis of the patients with MPNST. Although VEGF mRNA expression tended to be higher in MPNST compared to neurofibroma, the difference was not significant. Levels of VEGF protein expression serve as a novel diagnostic and prognostic tools for peripheral nerve sheath tumors.

  2. Sheath overlap during very large scale plasma source ion implantation

    NASA Astrophysics Data System (ADS)

    Cluggish, B. P.; Munson, C. P.

    1998-12-01

    Measurements of plasma source ion implantation have been performed on a large target of complex geometry. The target consists of 1000 aluminum, automotive piston surrogates mounted on four racks; total surface area is over 16 m2. The four racks are positioned parallel to each other, 0.25 m apart, in an 8 m3 vacuum chamber. The racks of pistons are immersed in a capacitive radio frequency plasma, with an argon gas pressure of 20-65 mPa. Langmuir probe measurements indicate that the plasma density profile is highly nonuniform, due to particle losses to the racks of pistons. The plasma ions are implanted into the pistons by pulse biasing the workpiece to negative voltages as low as -18 kV for up to 20 μs. During the voltage pulse, the high-voltage sheaths from adjacent racks of pistons converge towards each other. At plasma densities less than 109 cm-3 the sheaths are observed to overlap. Measurements of the sheath overlap time are compared with standard analytic theory and with simulations run with a two-dimensional particle-in-cell code.

  3. Dynamics of magnetized plasma sheaths around a trench

    SciTech Connect

    Hatami, M. M.

    2016-08-15

    Considering a magnetized plasma sheath, the temporal evolution of the ion properties (the incident ion flux, the ion impact angle, and the incident ion dose) around a rectangular trench is studied numerically. Our results show that the ion flux along the bottom surface greatly reduces in the presence of magnetic field and its uniformity improves, but the magnetic field does not considerably affect the ion flux along the sidewall. In addition, the thickness of the plasma sheath increases by increasing the magnetic field while its conformality to the target surface reduces faster. Moreover, it is shown that any increase in the magnitude (inclination angle) of the magnetic field causes a decrease (an increase) in the angle of incidence of ions on the bottom and sidewall surfaces. Furthermore, in the presence of magnetic field, the ions strike nearly normal to the surface of the bottom while they become less oblique along the sidewall surface. In addition, contrary to the corners of the trench, it is found that the magnetic field greatly affects the incident ion dose at the center of the trench surfaces. Also, it is shown that the incident ion dose along the sidewall is the highest near the center of the sidewall in both magnetized and magnetic-free cases. However, uniformity of the incident ion dose along the sidewall is better than that along the bottom in both magnetized and unmagnetized plasma sheath.

  4. Radio-frequency sheath voltages and slow wave electric field spatial structure

    SciTech Connect

    Colas, Laurent Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan

    2015-12-10

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the RF parallel electric field emitted by Ion Cyclotron (IC) wave launchers, using a simple model of Slow Wave (SW) evanescence coupled with Direct Current (DC) plasma biasing via sheath boundary conditions in a plasma-filled 2-dimensional (parallel, radial) rectangle. Within a “wide sheaths” asymptotic regime, valid for large-amplitude near RF fields, our model becomes partly linear: the sheath oscillating voltage at open field line boundaries is a linear combination of elementary contributions by every source point of the radiated RF field map. These individual contributions are all the more intense as the SW emission point is toroidally nearer to the sheath walls. A limit formula is given for a source infinitely close to the sheaths. The decay of sheath RF voltages with the sheath/source parallel distance is quantified as a function of two characteristic SW evanescence lengths. Decay lengths are smaller than antenna parallel extensions. The sheath RF voltages at an IC antenna side limiter are therefore mainly sensitive to SW emission near this limiter, as recent observations suggest. Toroidal proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel anti-symmetry of the radiated field map. They could also justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  5. A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

    DOE PAGES

    Kohno, H.; Myra, J. R.

    2017-07-24

    A finite element code that solves self-consistent radio-frequency (RF) sheath-plasma interaction problems is improved by incorporating a generalized sheath boundary condition in the macroscopic solution scheme. This sheath boundary condition makes use of a complex sheath impedance including both the sheath capacitance and resistance, which enables evaluation of not only the RF voltage across the sheath but also the power dissipation in the sheath. The newly developed finite element procedure is applied to cases where the background magnetic field is perpendicular to the sheath surface in one- and two-dimensional domains filled by uniform low- and high-density plasmas. The numerical resultsmore » are compared with those obtained by employing the previous capacitive sheath model at a typical frequency for ion cyclotron heating used in fusion experiments. It is shown that for sheaths on the order of 100 V in a high-density plasma, localized RF power deposition can reach a level which causes material damage. It is also shown that the sheath-plasma wave resonances predicted by the capacitive sheath model do not occur when parameters are such that the generalized sheath impedance model substantially modifies the capacitive character of the sheath. Here, possible explanations for the difference in the maximum RF sheath voltage depending on the plasma density are also discussed.« less

  6. Core-sheath differentially biodegradable nanofiber structures for tissue engineering

    NASA Astrophysics Data System (ADS)

    Moghe, Ajit Keshav

    In recent years, it has been shown that the nanofiber structures prepared using electrospinning can serve as near ideal substrates for engineering tissues. Various biodegradable polymers of natural and synthetic origins have been used to construct the nanofiber scaffolds. The use of natural polymers is important in that they contain specific cell recognition sites that are capable of binding cells. Synthetic biodegradable polymers, on the other hand, can provide the necessary mechanical properties and their degradation rate can be controlled positively. When used alone, however, neither can provide an ideal structure for long-term development of tissues. This is because the regenerated natural polymers, although greatly biocompatible, are weak and degrade rapidly and uncontrollably, while the synthetic polymers, although mechanically more stable, are not as biocompatible. The focus of the current investigation was, therefore, to combine natural and synthetic polymers and to produce materials that have novel hybrid properties at the nano level. An optimum structure proposed was a differentially biodegradable bicomponent nanofiber with the sheath of natural and the core of synthetic polymers. Co-axial electrospinning was used to prepare the proposed core-sheath nanofibers. A major objective of the current research was to develop and optimize the technology to produce uniform bicomponent nanofibers of predictable morphologies by understanding the effects of various material and process variables such as solution concentration, solvent type, solution flow rate, and applied voltage. Two natural polymers (collagen and gelatin) and one synthetic biodegradable polymer (PCL) were used to develop the proposed structures. The factors that affected the bicomponent fiber formation were: interfacial tension between sheath and core solutions, volatility of the solvent, and applied voltage. By minimizing the interfacial tension, selecting the solvents with low vapor pressure, and

  7. The Relation of Carbon Dioxide Compensation and Chlorenchymatous Vascular Bundle Sheaths in Leaves of Dicots

    PubMed Central

    Crookston, R. Kent; Moss, Dale N.

    1970-01-01

    Low CO2 compensation points have been found to be associated with several unusual characteristics related to photosynthesis. One such characteristic is a prominent, chlorenchymatous vascular bundle sheath in the leaves. It has been suggested that the presence of this sheath in dicotyledons can serve as a means of detecting low CO2-compensating species. We collected 88 dicotyledon species from 22 families reported to have chlorenchymatous sheaths. Of the 88, only three, Tribulus terrestris, L., Boerhaavia paniculata, L. C. Rich, and Trianthema portulacastrum L., had low CO2 compensation points. Cross sections of the leaves of the other species revealed that they did have chlorenchymatous vascular bundle sheaths. However, these sheath cells contained chloroplasts which were not specialized for starch formation as were the bundle sheath chloroplasts of the low CO2-compensating species. Images PMID:16657506

  8. AC losses of single-core MgB2 wires with different metallic sheaths

    NASA Astrophysics Data System (ADS)

    Kováč, J.; Šouc, J.; Kováč, P.; Hušek, I.

    2015-12-01

    AC losses of single-core MgB2 superconductors with different metallic sheaths (Cu, GlidCop, stainless steel and Monel) have been measured and analyzed. These wires were exposed to external magnetic field with frequencies 72 and 144 Hz and amplitudes up to 0.1 T at temperatures ranged from 18 to 40 K. The obtained results have shown that applied metallic sheath can affect the measured AC loss considerably. In the case of GlidCop and Stainless Steel a negligible small effect of metallic sheath was observed. Strong contribution of eddy currents has been found in the wire with well conductive copper sheath. In the case of Monel sheath, the hysteresis loss of magnetic sheath is dominated and AC loss of MgB2 core is practically not visible.

  9. Up- and downstream sheaths in an ion-beam-plasma system

    SciTech Connect

    Wei, Zi-an; Ma, J. X.

    2016-02-15

    Ion sheaths formed in the up- and downstream sides of a negatively biased metal plate/mesh in an ion-beam-background-plasma system were experimentally investigated in a double plasma device. Measured potential profiles near the plate exhibit asymmetric structure, showing thicker sheath in the downstream side. The presence of the ion beam causes the shrink of the sheaths on both sides. The sheath thickness decreases with the increase of beam energy and density. Furthermore, the sheaths near the mesh are substantially thinner than that near the plate because of the partial transmission of the mesh to the ions. In addition, the increase of neutral gas pressure leads to the reduction of the beam energy and density, resulting in the increase of the sheath thickness.

  10. Model and particle-in-cell simulation of ion energy distribution in collisionless sheath

    SciTech Connect

    Zhou, Zhuwen; Kong, Bo; Luo, Yuee; Chen, Deliang; Wang, Yuansheng

    2015-06-15

    In this paper, we propose a self-consistent theoretical model, which is described by the ion energy distributions (IEDs) in collisionless sheaths, and the analytical results for different combined dc/radio frequency (rf) capacitive coupled plasma discharge cases, including sheath voltage errors analysis, are compared with the results of numerical simulations using a one-dimensional plane-parallel particle-in-cell (PIC) simulation. The IEDs in collisionless sheaths are performed on combination of dc/rf voltage sources electrodes discharge using argon as the process gas. The incident ions on the grounded electrode are separated, according to their different radio frequencies, and dc voltages on a separated electrode, the IEDs, and widths of energy in sheath and the plasma sheath thickness are discussed. The IEDs, the IED widths, and sheath voltages by the theoretical model are investigated and show good agreement with PIC simulations.

  11. A Cytochemical Study of Extracellular Sheaths Associated with Rigidoporus lignosus during Wood Decay

    PubMed Central

    Nicole, M.; Chamberland, H.; Rioux, D.; Lecours, N.; Rio, B.; Geiger, J. P.; Ouellette, G. B.

    1993-01-01

    An ultrastructural and cytochemical investigation of the development of Rigidoporus lignosus, a white-rot fungus inoculated into wood blocks, was carried out to gain better insight into the structure and role of the extracellular sheaths produced by this fungus during wood degradation. Fungal sheaths had a dense or loose fibrillar appearance and were differentiated from the fungal cell wall early after wood inoculation. Close association between extracellular fibrils and wood cell walls was observed at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep in host cell walls, sometimes enclosing residual wood fragments. Specific gold probes were used to investigate the chemical nature of R. lignosus sheaths. While labeling of chitin, pectin, β-1,4- and β-1,3-glucans, β-glucosides, galactosamine, mannose, sialic acid, RNA, fucose, and fimbrial proteins over fungal sheaths did not succeed, galactose residues and laccase (a fungal phenoloxidase) were found to be present. The positive reaction of sheaths with the PATAg test indicates that polysaccharides such as β-1,6-glucans are important components. Our data suggest that extracellular sheaths produced by R. lignosus during host cell colonization play an important role in wood degradation. Transportation of lignin-degrading enzymes by extracellular fibrils indicates that alteration of plant polymers may occur within fungal sheaths. It is also proposed that R. lignosus sheaths may be involved in recognition mechanisms in fungal cell-wood surface interactions. Images PMID:16349017

  12. The spatiotemporal oscillation characteristics of the dielectric wall sheath in stationary plasma thrusters

    SciTech Connect

    Zhang Fengkui; Yu Daren; Ding Yongjie; Li Hong

    2011-03-14

    A two-dimensional particle in cell model is used to simulate the sheath oscillation in stationary plasma thrusters. The embedded secondary electron emission (SEE) submodel is based on that of Morozov but improved by considering the electron elastic reflection effect. The simulation results show that when the SEE coefficient is smaller than one due to the relative low electron temperature, one-dimensional static sheath can be found; as the electron temperature increase, the SEE coefficient approaches to one and temporal oscillation sheath appears; when the electron temperature increases so high that the SEE coefficient is beyond one, the sheath oscillates not only in time but also in space.

  13. Development of a core sheath process for production of oxide fibers

    NASA Technical Reports Server (NTRS)

    Freske, S.

    1972-01-01

    Improvements were sought in an oxide fiber of a core sheath configuration intended for structural applications at 2000 F (1093 C). Discontinuities in the core were eliminated by using core materials other than pure alumina, and continuous core sheath fibers were produced. In the case of some core materials, the continuous sections were sufficiently long for applications in short fiber composites. Creep at 2000 F (1093 C) was found to be due, in most cases, to breaks in the core, allowing the glass sheath to creep. Evidence was obtained indicating that a closer match between the thermal expansion coefficient of the sheath and the core would greatly improve the strength.

  14. Sheath and presheath in ion-ion plasmas via particle-in-cell simulation

    SciTech Connect

    Meige, A.; Leray, G.; Raimbault, J.-L.; Chabert, P.

    2008-02-11

    A full particle-in-cell simulation is developed to investigate electron-free plasmas constituted of positive and negative ions under the influence of a dc bias voltage. It is shown that high-voltage sheaths following the classical Child-law sheaths form within a few microseconds (which corresponds to the ion transit time) after the dc voltage is applied. It is also shown that there exists the equivalent of a Bohm criterion where a presheath accelerates the ions collected at one of the electrodes up to the sound speed before they enter the sheath. From an applied perspective, this leads to smaller sheaths than one would expect.

  15. The dust motion inside the magnetized sheath - The effect of drag forces

    SciTech Connect

    Pandey, B. P.; Samarian, A.; Vladimirov, S. V.

    2010-08-15

    The isolated charged dust inside the magnetized plasma sheath moves under the influence of the electron and ion drag force and the sheath electrostatic field. The charge on the dust is a function of its radius as well as the value of the ambient sheath potential. It is shown that the charge on the dust determines its trajectory and dust performs the spiraling motion inside the sheath. The location of the turning spiral is determined by the number of negative charge on the dust, which in turn is a function of the dust radius. The back and forth spiraling motion finally causes the dust to move in a small, narrow region of the sheath. For a bigger dust particle, the dust moves closer to the sheath presheath boundary suggesting that the bigger grains, owing to the strong repulsion between the wall and dust, will be unable to travel inside the sheath. Only small, micron-sized grains can travel closer to the wall before repulsion pushes it back toward the plasma-sheath boundary. The temporal behavior of the spiraling dust motion appears like a damped harmonic oscillation, suggesting that the plasma drag force causes dissipation of the electrostatic energy. However, after initial damping, the grain keeps oscillating although with much smaller amplitude. The possible application of the present results to the ongoing sheath experiments is discussed.

  16. The modeling and simulation of plasma sheath effect on GNSS system

    NASA Astrophysics Data System (ADS)

    Song, Zhongguo; Liu, Jiangfan; Du, Yongxing; Xi, Xiaoli

    2015-11-01

    Plasma sheath can potentially degrade global navigation satellite system (GNSS) through signal attenuation as well as phase noise when a hypersonic vehicle reenters the Earth's atmosphere. Modeling and simulation method of GNSS system disturbed by plasma sheath is introduced in this paper by means of electromagnetic wave propagation theory combined with the satellite signal simulation technique. The transmission function of the plasma sheath with stratified model is derived utilizing scattering matrix method. The effects of the plasma sheath on GPS signal reception and positioning performance are examined. Experimental results are presented and discussed, partly supporting the validity of the analytical method proposed.

  17. Thrombus on Indwelling Central Venous Catheters: The Histopathology of 'Fibrin Sheaths'

    SciTech Connect

    Suojanen, James Norman; Brophy, David Paul; Nasser, Imad

    2000-03-15

    Purpose: Central venous catheters (CVC) may fail for many reasons, though 'fibrin sheaths' blocking catheter ports are usually implicated. We examined the sheaths removed from dialysis catheters to determine their histopathology.Methods: Ten catheter strippings were performed and the removed material was studied grossly and microscopically.Results: The histologic specimens showed thrombus both with and without a proteinaceous sheath.Conclusion: Dialysis catheters fail because of thrombus formation. This can occur in either the absence or presence of a protein coating on the catheter, the so-called 'fibrin sheath.'.

  18. Finite Element Biomechanics of Optic Nerve Sheath Traction in Adduction.

    PubMed

    Shin, Andrew; Yoo, Lawrence; Park, Joseph; Demer, Joseph L

    2017-10-01

    Historical emphasis on increased intraocular pressure (IOP) in the pathogenesis of glaucoma has been challenged by the recognition that many patients lack abnormally elevated IOP. We employed finite element analysis (FEA) to infer contribution to optic neuropathy from tractional deformation of the optic nerve head (ONH) and lamina cribrosa (LC) by extraocular muscle (EOM) counterforce exerted when optic nerve (ON) redundancy becomes exhausted in adduction. We characterized assumed isotropic Young's modulus of fresh adult bovine ON, ON sheath, and peripapillary and peripheral sclera by tensile elongation in arbitrary orientations of five specimens of each tissue to failure under physiological temperature and humidity. Physical dimensions of the FEA were scaled to human histological and magnetic resonance imaging (MRI) data and used to predict stress and strain during adduction 6 deg beyond ON straightening at multiple levels of IOP. Young's modulus of ON sheath of 44.6 ± 5.6 MPa (standard error of mean) greatly exceeded that of ON at 5.2 ± 0.4 MPa, peripapillary sclera at 5.5 ± 0.8 MPa, and peripheral sclera at 14.0 ± 2.3 MPa. FEA indicated that adduction induced maximum stress and strain in the temporal ONH. In the temporal LC, the maximum stress was 180 kPa, and the maximum strain was ninefold larger than produced by IOP elevation to 45 mm Hg. The simulation suggests that ON sheath traction by adduction concentrates far greater mechanical stress and strain in the ONH region than does elevated IOP, supporting the novel concept that glaucomatous optic neuropathy may result at least partly from external traction on the ON, rather than exclusively on pressure on the ON exerted from within the eye.

  19. Low-current medium-pressure RF discharge with electron photoemission in the electrode sheath and penetration of the sheath electrons into the discharge column

    SciTech Connect

    Baranov, I. Ya.; Koptev, A. V.

    2007-12-15

    A model is developed for simulating a low-current moderate-pressure RF discharge with allowance for such characteristic discharge properties as the existence of two sheaths near both electrodes throughout the RF field period; the formation of an electron cloud at the sheath boundary that periodically fills the sheath and leaves it, depending on the phase of the applied RF voltage; the production by the sheath electrons of metastable gas particles that interact with the cloud electrons during subsequent field periods, followed by the excitation of metastable states to the emitting levels; the formation of a sheath in a low-current RF discharge due to the overlap of the secondary electron avalanches triggered by electron photoemission from the electrode surface; and the conditions under which the sheath electrons penetrate into the positive column and accumulate there, which makes, thereby making a low-current RF discharge similar to a non-self-sustained discharge. The parameters of the sheath in a low-current RF discharge are determined by the conditions under which the electron photoemission current from the electrode surface in the sheath is self-sustaining and, like the parameters of the positive discharge column, depend on the sort of gas, the gas pressure, the frequency of the applied RF field, and the interelectrode distance. The results of calculating the parameters of the sheath and column of a low-current RF discharge for nitrogen and helium at different pressures, as well as for different field frequencies and interelectrode distances, are presented and are compared with the experimental data.

  20. Retracted: Spontaneous rectus sheath haematoma associated with rivaroxaban treatment.

    PubMed

    Tas Tuna, A; Palabiyik, O; Beyaz, S G

    2015-08-01

    http://onlinelibrary.wiley.com/doi/10.1111/jcpt.12228/pdf The above article, published online on 10 November 2014 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, A. Li Wan Po, and John Wiley & Sons Ltd. The retraction has been agreed because, unknown to the authors, another group published a similar study based on the same material in the Indian Journal of Pharmacology: Kocayigit I, Can Y, Sahinkus S, et al. Spontaneous rectus sheath haematoma during rivaroxaban therapy. Indian Journal of Pharmacology. 2014;46(3):339-340. doi:10.4103/0253-7613.132193.

  1. Silver sheathing of high-T sub c superconductor wires

    SciTech Connect

    Wu, C.T. ); Risch, G.A.; Poeppel, R.B.; Goretta, K.C. ); Danyluk, S. ); Herro, H.M. ); McGuire, M.J. Illinois Univ., Chicago, IL )

    1990-10-01

    The properties of Ag sheaths on high-temperature super-conductors are examined. Ag is chemically compatible with YBa{sub 2}Cu{sub 3}O{sub x} and Bi-based superconductors can be safely coprocessed with them. Residual stresses created by differences in thermal expansion coefficients are favorable and can be controlled by proper annealing. Although Ag forms low-resistance contact with high-temperature superconductors, it is not certain that effective cryogenic stabilization by Ag can occur at 77 K and above. 42 refs., 7 figs.

  2. Optic nerve sheath meningioma: current diagnosis and treatment.

    PubMed

    Eddleman, Christopher S; Liu, James K

    2007-01-01

    Optic nerve sheath meningiomas (ONSMs) are rare tumors of the anterior visual pathway and constitute approximately 2% of all orbital tumors and 1-2% of all meningiomas. Untreated ONSMs almost always lead to progressive visual decline, color blindness, and finally complete loss of vision. Although resection is warranted in cases of widespread ONSM, surgery can lead to significant morbidity. Recently, stereotactic fractionated radiotherapy has shown effectiveness in improving or stabilizing remaining visual function with minimal procedural morbidity in patients with ONSM. The authors review the incidence, histopathological characteristics, clinical presentation, neuroimaging findings, and current treatment modalities for ONSMs, with an emphasis on fractionated stereotactic radiotherapy.

  3. Spine+Sheath AGN with Helical B-Field Structure?

    NASA Astrophysics Data System (ADS)

    Reichstein, A.; Gabuzda, D.

    2010-10-01

    We analyze multi-frequency radio observations obtained on the Very Long Baseline Array (VLBA) of selected AGN, that seem to have a B-field structure with a central "spine" of B-field orthogonal to the jet and a longitudinal B-field near one or both edges of the jet. Two explanations for this structure have been discussed in the literature: shocks making the central orthogonal field combined with a jet-medium interaction making a "sheath" of longitudinal field, or both components produced by a helical magnetic field. We will discuss evidence from our observations supporting the latter of these two pictures.

  4. Characterization of the Biomechanical Behavior of the Optic Nerve Sheath

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Wang, Roy; Forte, Taylor E.; Feola, Andrew; Samuels, Brian; Myers, Jerry; Nelson, Emily; Gleason, Rudy; Ethier, C. Ross

    2016-01-01

    A major priority in current space medicine research is to characterize the mechanisms in Visual Impairment and Intracranial Pressure (VIIP) syndrome, a group of ophthalmic changes that occur in some astronauts following long-duration spaceflight [1]. It is hypothesized that microgravity-induced cephalad fluid shifts lead to increases in intracranial pressure (ICP), which drives maladaptive remodeling of the optic nerve sheath (ONS). In this study, we investigated the effects of mechanical loading on the porcine ONS to better understand the mechanical response of the ONS to increased ICP.

  5. Dust Particles Alignments and Transitions in a Plasma Sheath

    SciTech Connect

    Stokes, J. D. E.; Samarian, A. A.; Vladimirov, S. V.

    2008-09-07

    The alignments and transitions of two dust particles in a plasma sheath have been investigated. It is shown that the Hamiltonian description of a non-Hamiltonian system can be used to predict qualitative features of possible equilibria in a variety of confinement potentials and can provide useful plasma diagnostics. The results compare favorably with simulation and are used to create new experimental hypotheses. In particular, the symmetry breaking transition of the particles as they leave the horizontal plane admits a Hamiltonian description which is used to elucidate the wake parameter.

  6. Balloon angioplasty for disruption of tunneled dialysis catheter fibrin sheath.

    PubMed

    Watorek, Ewa; Golebiowski, Tomasz; Letachowicz, Krzysztof; Garcarek, Jerzy; Kurcz, Jacek; Bartosik, Hanna Augustyniak; Letachowicz, Waldemar; Weyde, Waclaw; Klinger, Marian

    2012-01-01

    Management of failing tunneled hemodialysis catheters, sometimes the only vascular access for hemodialysis, presents a difficult problem. In spite of various techniques having been developed, no consensus has been reached about the preferred technique, associated with the longest catheter patency. We report disruption of the fibrin sheath covering dysfunctional tunneled hemodialysis catheter by means of angioplasty, followed by over guidewire catheter exchange. Following the procedure, the catheter placed in the recovered lumen of the vessel presented correct function. The described procedure allowed maintenance of vascular access in our patient. Additionally, dilatation of the concomitant central vein stenosis opens an option for another attempt for arteriovenous fistula creation.

  7. Microparticles deep in the plasma sheath: Coulomb 'explosion'

    SciTech Connect

    Antonova, T.; Du, C.-R.; Ivlev, A. V.; Hou, L.-J.; Thomas, H. M.; Morfill, G. E.; Annaratone, B. M.

    2012-09-15

    A cloud of microparticles was trapped deep in the sheath of a radio-frequency (rf) discharge, very close to the lower (grounded) electrode of the plasma chamber. This was achieved by employing a specifically designed rf-driven segment integrated in the lower electrode, which provided an additional confinement compressing the cloud to a very high density. After switching the rf-driven segment off, the cloud 'exploded' due to mutual interparticle repulsion. By combining a simple theoretical model with different numerical simulation methods, some basic properties of complex plasmas in this highly non-equilibrium regime were determined.

  8. Mechanical Thrombectomy of Iliocaval Thrombosis Using a Protective Expandable Sheath

    SciTech Connect

    Truong, Tri H.; Spuentrup, Elmar; Staatz, Gundula; Wildberger, Joachim E.; Schmitz-Rode, Thomas; Nolte-Ernsting, Claus C.A.; Guenther, Rolf W.; Haage, Patrick

    2004-09-15

    We report a case of successful percutaneous treatment of a subacute ilio-caval venous thrombosis in a 64-year-old female patient by using a novel combination of a rotatory fragmentation device (percutaneous thrombectomy device: PTD) and large wire basket (temporary Guenther basket filter) under temporary caval filter protection using an expandable sheath. Because the patient had multiple myeloma with increased risk for contrast media-induced renal failure, the therapeutic angiographic procedure was performed without iodinated contrast medium. Non-contrast-enhanced MR venography (high-resolution True FISP) confirmed the effective thrombus removal by the percutaneous mechanical thrombectomy procedure.

  9. Cystic change in primary paediatric optic nerve sheath meningioma.

    PubMed

    Narayan, Daniel; Rajak, Saul; Patel, Sandy; Selva, Dinesh

    2016-08-01

    Primary optic nerve sheath meningiomas (PONSM) are rare in children. Cystic meningiomas are an uncommon subgroup of meningiomas. We report a case of paediatric PONSM managed using observation alone that underwent cystic change and radiological regression. A 5-year-old girl presented with visual impairment and proptosis. Magnetic resonance (MR) imaging demonstrated a PONSM. The patient was left untreated and followed up with regular MR imaging. Repeat imaging at 16 years of age showed the tumour had started to develop cystic change. Repeat imaging at 21 years of age showed the tumour had decreased in size.

  10. Ionization Induced Instability in an Electron Collecting Sheath,

    DTIC Science & Technology

    1985-06-01

    shown to be equivalent to a mean free path for ionization by electrons "Xie < 6iiii ’ ( DS /aJ’ where DS is the sheath thickness and at is a- geometry...CLASSIFICATION UNCLASSIFOEO/UNLIMI1TEO - SAME AS RPT IDTIC USERS .UNCLASSIFIED 22a. ’JAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE NUMBER 22c CFF CE SyABCL Michael...anode does not emit, then we have the usual planar Child -Langmuir diode ( Child , 1911; Langmuir, 1913) where the separation DCL, potential drop V, and

  11. [Intrathoracic giant peripheral nerve sheath tumor during Von Recklinghausen disease].

    PubMed

    Ngabou, U D; Mounguengui, D; Owono Mbouengou, J P; El Wali, A; Nguema Edzang, B; Boguikouma, J B; Tchoua, R; Aziz, N E

    2014-06-01

    We report the case of a patient aged 23, admitted for bilateral intrathoracic tumor, including a giant right. Surgery was performed by right sternothoracotomy. After 7 days, she presented an irreversible cardiac arrest. The malignant peripheral nerve sheath tumors are rare and aggressive. Their incidence is 0.001% in the general population and 0.16% in patients with neurofibromatosis type 1. These tumors are characterized by their risk of recurrence and poor prognosis. The treatment is the surgical resection. We analyze incidence, diagnosis and prognosis of these tumors.

  12. Intrarenal pressure and irrigation flow with commonly used ureteric access sheaths and instruments

    PubMed Central

    Wright, Anna; Williams, Kevin; Somani, Bhaskar

    2015-01-01

    Introduction Flexible ureterorenoscopy is becoming a first-line treatment for many intrarenal stones. Ureteric access sheaths are commonly used to aid access, stone removal and reduce intrarenal pressure. We evaluated the effects of two commonly used access sheaths on irrigation flow and intrarenal pressure during flexible ureterorenoscopy. We measured the effect of scope instrumentation on flow and pressure. Material and methods We utilized a 10/12F and 12/14F, 35 cm Re-Trace™ access sheath with a FlexX2 scope in a cadaveric porcine kidney. We evaluated the effect of four Nitinol baskets (1.3F, 1.5F, 1.9F, 2.2F), three different 200 µm laser fibres and a hand-held pump. Measurements of irrigation flow and intrarenal pressure were recorded and compared between the different sized access sheaths. Results Flow rates varied widely between access sheaths. Without instrumentation, mean flow was 17 mls/min (10/12F access sheath), versus 33 mls/min (12/14F sheath) (p <0.0001). Increasing basket size produced a gradual reduction in flow and pressure in both access sheaths. Reassuringly, pressures were low overall (<40 cm H2O). Pressures were significantly reduced when using the larger 12/14F sheath, with and without all instrumentations (p <0.0001). Hand-held pump devices have a marked effect on flow and pressure in both sheaths; with pressures rising up to 121 cm H2O with a 10/12F sheath, versus 29 cm H2O (12/14F) (p <0.0001). Conclusions A 12/14F access sheath offered significantly improved irrigation whilst maintaining significantly lower intrarenal pressure, when compared to a 10/12F access sheath in a cadaveric porcine model. Scope instrumentation affects irrigation flow and pressure in both sized sheaths. Furthermore, there should be caution with hand-held pump devices, especially with smaller sized sheaths, as intrarenal pressure can be very high. PMID:26855796

  13. Ion flow and sheath structure near positively biased electrodes

    NASA Astrophysics Data System (ADS)

    Hood, Ryan; Scheiner, Brett; Baalrud, Scott; Hopkins, Matthew; Barnat, Ed; Yee, Benjamin; Merlino, Robert; Skiff, Fred

    2016-10-01

    Measurements of the ion velocity distribution function (IVDF) and plasma potential were made near small positively biased electrodes using laser-induced fluorescence (LIF) and an emissive probe. The effect of dielectric around the electrode was tested and compared with a 2D particle-in-cell (PIC) simulation. Both measurements and simulation reveal that if the electrode is embedded within a surrounding dielectric, ions are accelerated toward the electrode to approximately 0.5 times the ion sound speed before being deflected radially by the electron sheath potential barrier. The axial potential profile in this case contains a virtual cathode. In comparison, when the surrounding dielectric is removed, both the ion flow and virtual cathode depth are dramatically reduced. These measurements suggest that the ion presheath from the dielectric may enclose the electron sheath of the electrode resulting in a virtual cathode that substantially influences the local ion flow profile. This research was supported by the Office of Fusion Energy Sciences at the U.S. Department of Energy under contract DE-AC04-94SL85000.

  14. Test ion acceleration in a dynamic planar electron sheath

    NASA Astrophysics Data System (ADS)

    Basko, M. M.

    2007-03-01

    New exact results are obtained for relativistic acceleration of test positive ions in the laminar zone of a planar electron sheath evolving from an initially mono-energetic electron distribution. The electron dynamics is calculated against the background of motionless foil ions. The limiting gamma-factor γp∞ of accelerated ions is shown to be determined primarily by the values of the ion-electron charge-over-mass ratio μ=meZp/mp and the initial gamma-factor γ0 of the accelerated electrons. For μ> 1/8 a test ion always overtakes the electron front and attains γp∞> γ0. For μ< 1/8 a test ion can catch up with the electron front only when γ0 is above a certain critical value γcr, which for μ≪1 can most often be evaluated as γ_{cr} = ({1}/{4}) μexpleft(μ^{-1}-1right). In this model the protons and heavier test ions, for which γcr> 10398 is enormous, always lag behind the front edge of the electron sheath and have γp∞< γ0; for their maximum energy an appropriate intermediate asymptotic formula is derived. The domain of applicability of the laminar-zone results is analyzed in detail.

  15. Which ureteral access sheath is compatible with your flexible ureteroscope?

    PubMed

    Al-Qahtani, Saeed M; Letendre, Julien; Thomas, Alexandre; Natalin, Ricardo; Saussez, Thibaud; Traxer, Olivier

    2014-03-01

    Our aim is to evaluate different ureteral access sheaths (UASs), which are available in the international market and their compatibility with different available flexible ureteroscopes (F-URSs) to help the urologist choose the proper ureteral access sheath for his or her endoscope before commencing the procedure. A total of 21 UASs and 12 F-URSs were evaluated. Measurements were obtained in French (F) units considering different characteristics for each UAS and each F-URS. Insertion test without friction between F-URS and UAS was considered as a successful test and was referred as (YES). All UASs and F-URSs were successfully submitted to the insertion test. All F-URSs that were inserted into UASs without friction had an internal diameter of at least 12F. Different lengths of UAS did not influence the test outcome. This study was able to establish a correlation table between different UASs and different flexible ureteroscopes. As of now, the 12/14F UAS is considered the universal UAS that accepts all F-URSs that are available in the endourology field. Nevertheless, we are expecting a significant change with the new standard size 10/12F UAS as well as huge advances in minimizing the size of different endoscopes.

  16. Kinetic Effects on Plasma Blob Dynamics with Plasma Sheath

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hiroki; Ishiguro, Seiji

    2015-11-01

    Kinetic effects on plasma blob dynamics with plasma sheath have been studied with a three dimensional electrostatic plasma particle simulation code. In the particle simulation, an external magnetic field B is pointing into the z direction (corresponding to the toroidal direction). The strength of ambient magnetic field increases in the positive x direction (corresponding to the counter radial direction), i.e., ∂B / ∂x > 0 . A coherent structure is initially set as a column along the external magnetic field. In our previous study, we investigated kinetic effects on plasma blob dynamics in the system where the periodic boundary condition is applied in the z direction and found that the symmetry breaking in a blob profile occurs by the kinetic effect. In this study, we have applied the particle absorbing boundaries to the ends in the z direction and studied such kinetic effects with the plasma sheath. In the simulation, not only the symmetry breaking shown in the previous study but also other properties which were not found in the periodic boundary case have been observed. Supported by NIFS Collaboration Research programs (NIFS13KNSS038, NIFS15KNSS058, and NIFS14KNXN279) and a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science (KAKENHI 23740411).

  17. Measure Guideline: Guidance on Taped Insulating Sheathing Drainage Planes

    SciTech Connect

    Grin, A.; Lstiburek, J.

    2014-09-01

    This guide provides information and recommendations to the following groups: insulation contractors; general contractors; builders; home remodelers; mechanical contractors; and homeowners, as a guide to the work that needs to be done. The order of work completed during home construction and retrofit improvements is important. Health and safety issues must be addressed first and are more important than durability issues. And durability issues are more important than saving energy. Not all techniques can apply to all houses. Special conditions will require special action. Some builders or homeowners will wish to do more than the important but basic retrofit strategies outlined by this guide. The following are best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience. Three significant items were discussed with the group which are required to make taped insulating sheathing a simple, long term, and durable drainage plane: 1. Horizontal joints should be limited or eliminated wherever possible; 2. Where a horizontal joint exists use superior materials; 3. Frequent installation inspection and regular trade training are required to maintain proper installation. Section 5 of this measure guideline contains the detailed construction procedure for the three recommended methods to effectively seal the joints in exterior insulating sheathing to create a simple, long term, and durable drainage plane.

  18. Impact of sheath diameter of different sheath types on vascular complications and mortality in transfemoral TAVI approaches using the Proglide closure device

    PubMed Central

    Dimitriadis, Zisis; Scholtz, Werner; Ensminger, Stephan M.; Piper, Cornelia; Bitter, Thomas; Wiemer, Marcus; Vlachojannis, Marios; Börgermann, Jochen; Faber, Lothar; Horstkotte, Dieter; Gummert, Jan; Scholtz, Smita

    2017-01-01

    Objective Evaluation of the impact of the sheath diameter on vascular complications and mortality in transfemoral aortic valve implantation. Method Between 2012 and 2014, 183 patients underwent the procedure using a sheath diameter of 18–24 F. This collective was divided into two groups: group 1, with a sheath diameter of 18F (G1, n = 94), consisted of patients with 18F Medtronic Sentrant and 18 F Direct Flow sheaths, and group 2 with a sheath diameter of 19–24 F (G2, n = 89) consisted of patients with Edwards expandable e-sheath and Solopath sheaths. Perclose-Proglide® was used as a closure device in all patients. Results G1 had significantly more female patients (64.9% vs. 46.1% in G2, p = 0.01) and the average BMI was lower (26 ± 4.5% vs. 27.4 ± 4.7%, p = 0.03). There was no significant difference in the incidence of major and minor vascular complications (G1: 12.8% vs. G2: 12.4%, p = 0.9). 30-day mortality was similar in both groups (G1: 6.4 ± 2.5% [95% CI: 0.88–0.98], G2: 3.7 ± 1.9% [95% CI: 0.92–0.99]. The Kaplan Meier analysis of survival revealed no significant differences either. Conclusion The difference in sheath diameter had no effect on either incidence or severity of vascular complications. There was no impact on mortality either. PMID:28837613

  19. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... conduits enclosing power conductors. 75.700 Section 75.700 Mineral Resources MINE SAFETY AND HEALTH... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout...

  20. Dusty Plasma Modeling of the Fusion Reactor Sheath Including Collisional-Radiative Effects

    SciTech Connect

    Dezairi, Aouatif; Samir, Mhamed; Eddahby, Mohamed; Saifaoui, Dennoun; Katsonis, Konstantinos; Berenguer, Chloe

    2008-09-07

    The structure and the behavior of the sheath in Tokamak collisional plasmas has been studied. The sheath is modeled taking into account the presence of the dust{sup 2} and the effects of the charged particle collisions and radiative processes. The latter may allow for optical diagnostics of the plasma.

  1. Sheath and boundary conditions in a collisional magnetized warm electronegative plasma

    SciTech Connect

    Li, Jing-ju; Ma, J. X.; Wei, Zi-an

    2013-06-15

    The characteristics of a weakly collisional sheath in a warm electronegative plasma in the presence of an oblique magnetic field are investigated using a fluid model including the effects of ionization and ion-neutral collisions. The general sheath criterion imposed on the entrance velocity component of the positive ions perpendicular to the wall at the sheath-presheath edge is derived and discussed. It is shown that the boundary conditions are crucial to the sheath structure. Without including the entrance velocity components parallel to the wall, a pulse-like structure in the positive-ion density distribution near the sheath-presheath edge appears if the magnetic field is strong. With inclusion of all velocity components at the edge, the pulse-like structure disappears, resulting in a smooth sheath profile. It is also found that increasing the temperature and decreasing the concentration of the negative ions will increase the sheath thickness, and increasing the magnetic field will decrease the sheath thickness.

  2. Properties of the plasma sheath edge above a rectangular depression in DONUT

    NASA Astrophysics Data System (ADS)

    Steinberger, Thomas E.; Sheridan, T. E.

    2013-11-01

    Plasma is a gas consisting of positively and negatively charged particles, such as electrons and positive ions. The electric field inside a plasma is very small since plasma is a conductor. When plasma is in contact with a material boundary (i.e., a ``wall'') a boundary layer called the plasma sheath forms. The electric field inside the sheath is large and points away from the wall. The sheath electric field reduces the loss of highly mobile electrons, while accelerating ions out of the plasma, so that in steady state the electron and ion loss rates balance. The shape of the sheath edge is determined by the shape of the wall and the width of the sheath. We report experimental measurements of sheath conformation to a rectangular depression in a flat horizontal electrode (i.e., ``the wall'') in the Dusty Ohio Northern University experimenT (DONUT) for various aspect ratios. Clusters of two microscopic dust particles float above the depression at the sheath edge. The horizontal shape of the sheath edge is determined from the horizontal center-of-mass frequencies for the dust particles. The vertical electric field is found from the force balance on the dust particles, and the local charge density is measured using the vertical center-of-mass frequency.

  3. Plasma-wall interaction in an electrostatic sheath of plasma containing a monoenergetic electron beam

    SciTech Connect

    Ou, Jing Zhao, Xiaoyun; Gan, Chunyun

    2016-04-15

    The plasma-wall interaction in the presence of a monoenergetic electron beam has been studied by taking into account the self-consistency among plasma transport in a collisionless electrostatic sheath, deposited energy flux at the wall and material thermal response for carbon and tungsten as wall materials. The variations of the potential drop across the sheath, ion velocity at the sheath edge, and surface temperature of material as a function of electron beam flux are explored in the presence of the electron emission. It is found that when electron beam does not dominate the sheath, potential drop across the sheath depends strongly on the material properties due to the impact of electron emission while the surface temperature of material shows monotonic variation. In the case of carbon wall, the electron beam may dominate the sheath at a certain electron beam concentration or energy. Under this circumstance, both the potential drop across the sheath and surface temperature of material demonstrate the sharp increasing transition. The development of local hot spot on the plasma facing material is caused by the enhanced ion energy flux instead of the electron beam energy flux. If the electron emission is not taken into account, as a smaller electron beam flux, both the potential drop across the sheath and surface temperature of material display the significant change and then it may be easier to develop for the local hot spot on the plasma facing material.

  4. Analytical expression for the sheath edge around wedge-shaped cathodes

    NASA Astrophysics Data System (ADS)

    Sheridan, T. E.

    2008-03-01

    The sheath is the boundary layer separating a quasi-neutral plasma from a material electrode. Understanding the sheath is important for numerous applications, including plasma-based ion implantation, plasma etching of semiconductors, plasma assisted electrostatic cleaning, and Langmuir probes. In a 1D planar geometry, the Child-Langmuir (CL) law describes the sheath when the bias on a negative electrode, i.e., a cathode, is much greater than the electron temperature. In this case, the sheath width s is an eigenvalue of the problem. In 2D, the sheath edge is an unknown line (an ``eigen-boundary") which is determined by a set of coupled, nonlinear, partial differential equations. I have found an expression for the sheath edge around a 2D wedge-shaped cathode with included angle θw. In polar coordinates (r,θ), the sheath edge is a solution of r(aθ)=as where s is the planar sheath width far from the corner and θw=2π- π/a, so that a=1/2 gives a knife edge, while a=2/3 gives a square corner. This result is verified by comparison with the numerical solutions of Watterson [P. A. Watterson, J. Phys. D 22, 1300 (1989)].

  5. Development and characterization of RiceCAP QTL mapping population for sheath blight resistance

    USDA-ARS?s Scientific Manuscript database

    RiceCAP is a USDA CSREES funded project that has as one of its main objectives developing genetic markers associated with sheath blight resistance. Sheath blight, caused by Rhizoctonia solani, is an important disease of rice in the southern US. Tolerance to the disease is quantitatively inherited an...

  6. Ion temperature and gas pressure effects on the magnetized sheath dynamics during plasma immersion ion implantation

    SciTech Connect

    Khoram, M.; Ghomi, H. Navab Safa, N.

    2016-03-15

    Here, a collisional magnetized plasma with finite ion temperature is considered to examine the effects of the ion temperature and gas pressure on the plasma-sheath dynamics. We use the two-fluid model of plasma-sheath where the nonlinear equations of a dynamic sheath are solved using a full implicit scheme of finite difference method along with some convenient initial and boundary conditions at the plasma center and target. It is found that the ion temperature only has a significant effect on the characteristics of low voltage sheath, while the gas pressure (collision rate) seriously affects the dynamic characteristics of the low and high voltage plasma-sheath. One can see, increasing the ion temperature in low voltage plasma-sheath causes to increase the temporal curve of the ion dose and the ion impact energy on the target, reduces the temporal curve of the sheath width, and has no any effect on the temporal curve of the ion incident angle on the target. However, rising the gas pressure in low and high voltage plasma-sheath reduces all of these temporal curves.

  7. Biology of a Pine Needle Sheath Midge, Contarinia Acuta Gagne (Diptera: Cecidomyiidae), on Loblolly Pine

    Treesearch

    Julie C. Weatherby; John C. Moser; Raymond J. Gagné; Huey N. Wallace

    1989-01-01

    The biology of a pine needle sheath midge, Contarinia acuta Gagné is described for a new host in Louisiana. This midge was found feeding within the needle sheath on elongating needles of loblolly pine, P. taeda L. Needle droop and partial defoliation were evident on heavily infested trees. Overwintering C. acuta...

  8. FURTHER OBSERVATIONS ON THE STRUCTURE OF MYELIN SHEATHS IN THE CENTRAL NERVOUS SYSTEM

    PubMed Central

    Peters, A.

    1964-01-01

    Direct evidence has been presented to confirm the existence of a spiral in the myelin sheaths of the central nervous system. An account of some of the variations in structure of central myelin sheaths has been given and it has been shown that the radial component of myelin sheaths has the form of a series of rod-like thickenings of the intraperiod line. These thickenings extend along the intraperiod line in a direction parallel to the length of the axon. The relative position of the internal mesaxon and external tongue of cytoplasm has been determined in a number of transverse sections of sheaths from the optic nerves of adult mice, adult rats, and young rats. In about 75 per cent of the mature sheaths examined, these two structures were found within the same quadrant of the sheath, so that the cytoplasm of the external tongue process tends to lie directly outside that associated with the internal mesaxon. The frequency with which the internal mesaxon and external tongue lie within the same quadrant of the sheath increases both with the age of the animal and with the number of lamellae present within a sheath. The possible significance of these findings is discussed. PMID:14126873

  9. Making vanadium-based radiation-resistant alloys for fast-neutron reactor pin sheaths

    NASA Astrophysics Data System (ADS)

    Votinov, S. N.; Kolotushkin, V. P.; Nikulin, S. A.; Turilina, V. Yu.

    2009-05-01

    The working conditions are considered for pin sheath materials for future fast-neutron reactors, as well as the scope for using various classes of material for the sheaths. Alloys of vanadium with titanium and chromium are found to have advantages for these conditions.

  10. Biceps tendon sheath effusion as a diagnostic clue to rotator cuff pathology.

    PubMed

    Yadav, Pankaj K; Shah, Bhavin; Shende, Amol; Rajesh, S

    2014-02-01

    The objective of this study was to evaluate the role of biceps tendon sheath effusion detected on ultrasound as a diagnostic clue to rotator cuff pathology. Despite being the most common cause of shoulder pain in adults early sonographic changes of rotator cuff tendinopathy are easy to miss. A total of 31 patients out of whom 27 had unilateral shoulder pain and 4 had bilateral complaints under- went ultrasonographic examination of shoulder joint using high frequency linear array transducer. Any fluid surrounding the long head of biceps tendon was noted followed by a careful search for any associated sonographic abnormality involving the rotator cuff. Eighteen out of the 35 had presence of fluid in their biceps tendon sheath. Twelve had presence of both biceps tendon sheath effusion and rotator cuff pathologies. Among 17 patients, who had no fluid in their biceps tendon sheath, only 2 had rotator cuff involvement whereas rest 15 had neither biceps tendon sheath fluid nor rotator cuff pathologies. A significant association was found between presence of fluid in long head of biceps tendon sheath and rotator cuff pathologies. Thus the most common finding observed in association with the presence of fluid around the long head of biceps tendon sheath in this study was tendinosis of rotator cuff. On ultrasonography simple presence of fluid around the long head of biceps tendon sheath demands careful examination of rotator cuff.

  11. The tail sheath structure of bacteriophage T4: a molecular machine for infecting bacteria

    SciTech Connect

    Aksyuk, Anastasia A.; Leiman, Petr G.; Kurochkina, Lidia P.; Shneider, Mikhail M.; Kostyuchenko, Victor A.; Mesyanzhinov, Vadim V.; Rossmann, Michael G.

    2009-07-22

    The contractile tail of bacteriophage T4 is a molecular machine that facilitates very high viral infection efficiency. Its major component is a tail sheath, which contracts during infection to less than half of its initial length. The sheath consists of 138 copies of the tail sheath protein, gene product (gp) 18, which surrounds the central non-contractile tail tube. The contraction of the sheath drives the tail tube through the outer membrane, creating a channel for the viral genome delivery. A crystal structure of about three quarters of gp18 has been determined and was fitted into cryo-electron microscopy reconstructions of the tail sheath before and after contraction. It was shown that during contraction, gp18 subunits slide over each other with no apparent change in their structure.

  12. Composite pheochromocytoma with a malignant peripheral nerve sheath tumor: Case report and review of the literature.

    PubMed

    Namekawa, Takeshi; Utsumi, Takanobu; Imamoto, Takashi; Kawamura, Koji; Oide, Takashi; Tanaka, Tomoaki; Nihei, Naoki; Suzuki, Hiroyoshi; Nakatani, Yukio; Ichikawa, Tomohiko

    2016-07-01

    Adrenal tumors with more than one cellular component are uncommon. Furthermore, an adrenal tumor composed of a pheochromocytoma and a malignant peripheral nerve sheath tumor is extremely rare. A composite pheochromocytoma with malignant peripheral nerve sheath tumor in a 42-year-old man is reported here. After adequate preoperative control, left adrenalectomy was performed simultaneously with resection of the ipsilateral kidney for spontaneous rupture of the left adrenal tumor. Pathological findings demonstrated pheochromocytoma and malignant peripheral nerve sheath tumor in a ruptured adrenal tumor. To date, there have been only four reported cases of composite pheochromocytoma with malignant peripheral nerve sheath tumor, so the present case is only the fifth case in the world. Despite the very poor prognosis of patients with pheochromocytoma and malignant peripheral nerve sheath tumors reported in the literature, the patient remains well without evidence of recurrence or new metastatic lesions at 36 months postoperatively. Copyright © 2012. Published by Elsevier Taiwan.

  13. Physics-based parametrization of the surface impedance for radio frequency sheaths

    DOE PAGES

    Myra, J. R.

    2017-07-07

    The properties of sheaths near conducting surfaces are studied for the case where both magnetized plasma and intense radio frequency (rf) waves coexist. The work is motivated primarily by the need to understand, predict and control ion cyclotron range of frequency (ICRF) interactions with tokamak scrape-off layer plasmas, and is expected to be useful in modeling rf sheath interactions in global ICRF codes. Here, employing a previously developed model for oblique angle magnetized rf sheaths [J. R. Myra and D. A. D’Ippolito, Phys. Plasmas 22, 062507 (2015)], an investigation of the four-dimensional parameter space governing these sheath is carried out.more » By combining numerical and analytical results, a parametrization of the surface impedance and voltage rectification for rf sheaths in the entire four-dimensional space is obtained.« less

  14. Physics-based parametrization of the surface impedance for radio frequency sheaths

    NASA Astrophysics Data System (ADS)

    Myra, J. R.

    2017-07-01

    The properties of sheaths near conducting surfaces are studied for the case where both magnetized plasma and intense radio frequency (rf) waves coexist. The work is motivated primarily by the need to understand, predict, and control ion cyclotron range of frequency (ICRF) interactions with tokamak scrape-off layer plasmas and is expected to be useful in modeling rf sheath interactions in global ICRF codes. Employing a previously developed model for oblique angle magnetized rf sheaths [J. R. Myra and D. A. D'Ippolito, Phys. Plasmas 22, 062507 (2015)], an investigation of the four-dimensional parameter space governing these sheath is carried out. By combining numerical and analytical results, a parametrization of the surface impedance and voltage rectification for rf sheaths in the entire four-dimensional space is obtained.

  15. An investigation of friction-based tendon sheath model appropriate for control purposes

    NASA Astrophysics Data System (ADS)

    Do, T. N.; Tjahjowidodo, T.; Lau, M. W. S.; Phee, S. J.

    2014-01-01

    The tendon sheath mechanism plays an important role in many robotic systems from surgical devices to robot hands. However, many unexpected properties such as nonlinear hysteresis and backlash, which appear in the tendon sheath system, cause major losses in force transmission. This report deals with the characterization of hysteresis phenomenon, which is attributed to the presence of frictional effects on its elements, in a tendon-sheath driven surgical robot. Unlike various approaches presented in the literature that utilized multiple lumped mass elements, this proposed approach models the tendon sheath as one element. A new dynamic friction model that allows accurate description of friction lag and hysteresis behavior in two regimes, i.e. presliding and sliding regimes, for a sheath in arbitrary configuration such as helical and spatial shape has been developed.

  16. Feline cutaneous nerve sheath tumours: histological features and immunohistochemical evaluations.

    PubMed

    Mandara, M T; Fabriani, E; Pavone, S; Pumarola, M

    2013-10-01

    Feline cutaneous nerve sheath tumours (CNSTs) are uncommonly reported in the skin, since they are underestimated relative to the more common spindle cell tumours of soft tissue. In this study, 26 nerve sheath tumours selected from 337 skin neoplasms of cats were examined. Histologically, they were classified into malignant (MPNSTs) and benign tumours (BPNSTs) based on degree of cellular atypia and polymorphism as well as mitotic rate and diffuse necrosis. CPNSTs were tipically characterised by Antoni A pattern, in some cases associated with Antoni B pattern. In the malignant peripheral nerve sheath tumours (MPNSTs) the polymorphism was marked, while it was mild to moderate in the benign forms (BPNSTs). In the MPNSTs the mitotic activity was generally higher than in the BPNSTs. In five cases, including three MPNSTs and two BPNSTs, there were multinucleated giant cells. Necrotic foci occurred in a BPNST and in two MPNSTs, while osseous/chondroid metaplasia was found in two cases. Immunohistochemically, all the tumours showed a marked diffuse vimentin expression. S-100 protein was expressed in 17 cases, including 81.8% of BPNSTs and 57.14% of MPNSTs. Twenty-five tumours expressed NSE and twenty-four cases showed immunoreaction for laminin. Thirteen tumours were positive for GFAP, while five tumours were positive for SMA. PGP 9.5 expression was detected in all cases, except for two MPNSTs. NGFR was expressed in eleven cases, including four MPNSTs and seven BPNSTs. Ki67 was expressed in twenty tumours without any relationship with morphologic malignancy of the neoplasm. In this case series we confirmed neoplastic spindloid cells with wavy cytoplasm arranged in compact areas, with occasional nuclear palisading or whirls, and interchanged with loosely arranged areas, as the morphological features supporting a diagnosis of CPNST. A constant concurrent expression of vimentin, NSE, and laminin might confirm the diagnosis of PNST in the absence of clear S-100 protein

  17. Particle trap to sheath contact for a gas-insulated transmission line having a corrugated outer conductor

    DOEpatents

    Fischer, William H.; Cookson, Alan H.; Yoon, Kue H.

    1984-04-10

    A particle trap to outer elongated conductor or sheath contact for gas-insulated transmission lines. The particle trap to outer sheath contact of the invention is applicable to gas-insulated transmission lines having either corrugated or non-corrugated outer sheaths. The contact of the invention includes an electrical contact disposed on a lever arm which in turn is rotatably disposed on the particle trap and biased in a direction to maintain contact between the electrical contact and the outer sheath.

  18. Double copper sheath multiconductor instrumentation cable is durable and easily installed in high thermal or nuclear radiation area

    NASA Technical Reports Server (NTRS)

    Mc Crae, A. W., Jr.

    1967-01-01

    Multiconductor instrumentation cable in which the conducting wires are routed through two concentric copper tube sheaths, employing a compressed insulator between the conductors and between the inner and outer sheaths, is durable and easily installed in high thermal or nuclear radiation area. The double sheath is a barrier against moisture, abrasion, and vibration.

  19. Studies of in aere formed stylet sheath from the Asian citrus psyllid (Diaphorina citri, Hemiptera: Psyllidae) and other phytophagous Hemiptera

    USDA-ARS?s Scientific Manuscript database

    Stylet sheath formation is a common feature among phytophagous hemipterans. These sheaths are considered essential to promote a successful feeding event of these piercing-sucking insects. The stylet sheath composition is unknown and it is suggested that it forms through interactions with external (h...

  20. Malignant peripheral nerve sheath tumour in a sow.

    PubMed

    Resende, Talita P; Pereira, Carlos E R; Vannucci, Fabio A; Araujo, Fernando S; dos Santos, José Lúcio; Cassali, Geovanni D; Damasceno, Karine A; Guedes, Roberto M C

    2015-09-25

    Nodular lung lesions in swine are frequently due to abscesses or granulomatous pneumonia. Although tumours are rarely reported in modern pig farming, they should be considered as a differential diagnosis when nodular lung lesions are found. A first-parity sow exhibiting respiratory signs was euthanized. Several whitish firm nodules, not encapsulated, ranging in diameter from 0.5 to 5 cm were present in all lung lobes. Microscopically, the nodules were composed of dense neoplastic cells, mainly in Antoni types A and B patterns, infiltrative and with development of emboli. All neoplastic cells stained positively by immunohistochemistry for vimentin and S-100 protein, with variable immunostaining for glial fibrillary acidic protein and stained negative for cytokeratin. Based on the gross, histological and immunohistochemical features, the tumor was diagnosed as malignant peripheral nerve sheath tumour.

  1. Optic Nerve Sheath Meningioma Masquerading as Optic Neuritis

    PubMed Central

    Alroughani, R.; Behbehani, R.

    2016-01-01

    Optic neuritis is a common presentation of demyelinating disorders such as multiple sclerosis. It typically presents with acute painful monocular vision loss, whereas chronic optic neuropathy can be caused by compressive lesions along the anterior visual pathway, genetic, toxic, or nutritional causes. We report an unusual presentation mimicking optic neuritis, which was subsequently diagnosed as optic nerve sheath meningioma (ONSM). Misinterpretation of white matter lesions on MRI of brain and the failure to image the optic nerves at the time of acute loss of vision led to the misdiagnosis of optic neuritis in this case. A comprehensive accurate history and ordering the appropriate imaging modality remain paramount in diagnosing progressive visual deterioration. PMID:26904329

  2. Study of malignant peripheral nerve sheath tumor in cerebellopontine angle.

    PubMed

    Hong, WenMing; Cheng, HongWei; Wang, XiaoJie; Hu, XiaoPeng; Feng, ChunGuo

    2014-01-01

    Malignant peripheral nerve sheath tumors (MPNSTs) are very rare soft tissue sarcomas, usually arising from somatic soft tissues or peripheral nerves. Primary MPNST of the cerebellopontine angle is extremely rare, with only a single case reported so far. Here, we report an unusual case of MPNST in cerebellopontine angle in a 25-year-old man presented with dizziness, left facial numbness, and tinnitus. After hospitalization, the tumor was treated with complete surgical excision followed by adjuvant chemotherapy and radiotherapy. Histologically, the tumor showed malignant spindle cells, which were with focal S-100 positivity on immunohistochemistry, and a diagnosis of the MPNST was made. This case is being reported for its rarity and presence in cerebellopontine and illustrated the difficulties in the diagnosis and treatment of MPNST, which to the best of our knowledge, has not been described before in the soft tissue sarcomas.

  3. Inoculation and scoring methods for rice sheath blight disease.

    PubMed

    Jia, Yulin; Liu, Guangjie; Park, Dong-Soo; Yang, Yinong

    2013-01-01

    Sheath blight disease of rice caused by the soilborne fungal pathogen Rhizoctonia solani has been a major disease of rice with a serious threat to stable rice production worldwide. Although various cultural practices have been used to manage the disease, it is advantageous and important to screen rice germplasm and identify resistant rice cultivars for more effective disease control. Recent advances in methods for the fungal inoculation and disease evaluation have enabled a better measurement of host resistance by minimizing confounding factors from plant architectures and environmental conditions. This chapter introduces five such methods: (1) detached leaf method; (2) micro-chamber method; (3) mist-chamber method; (4) parafilm sachet method; and (5) aluminum foil method. These methods are useful for screening and evaluating disease reactions of rice germplasm and facilitating the genetic mapping of disease resistance genes.

  4. Sarcoma of possible nerve sheath origin in a captive muskrat.

    PubMed

    Borucinska, J D; Trettel, J; Knibbs, D

    2000-07-01

    A captive adult female muskrat (Ondatra zibethicus) was found dead without previous signs of disease. At necropsy, abdominal organs were infiltrated with a poorly demarcated, soft, tan tissue. Microscopically this tissue was composed of neoplastic cells assuming two distinct growth characteristics consistent with Antoni A and B patterns. Ultrastructurally, the neoplastic cells were pleomorphic, lacked junctional devices, had abundant mitochondria and ergastoplasm, and frequently were closely associated with extracellular collagen. Immunocytochemical examination of tumor cells demonstrated sporadic expression of neuron specific enolase. Microscopic tumor metastases to the myocardium, ascending aorta, lungs and visceral pleura were present. This is the first report of a sarcoma compatible with a malignant peripheral nerve sheath tumor in a muskrat.

  5. Electron inertia effects on the planar plasma sheath problem

    SciTech Connect

    Duarte, V. N.; Clemente, R. A.

    2011-04-15

    The steady one-dimensional planar plasma sheath problem, originally considered by Tonks and Langmuir, is revisited. Assuming continuously generated free-falling ions and isothermal electrons and taking into account electron inertia, it is possible to describe the problem in terms of three coupled integro-differential equations that can be numerically integrated. The inclusion of electron inertia in the model allows us to obtain the value of the plasma floating potential as resulting from an electron density discontinuity at the walls, where the electrons attain sound velocity and the electric potential is continuous. Results from numerical computation are presented in terms of plots for densities, electric potential, and particles velocities. Comparison with results from literature, corresponding to electron Maxwell-Boltzmann distribution (neglecting electron inertia), is also shown.

  6. Precession of cylindrical dust particles in the plasma sheath

    SciTech Connect

    Banu, N.; Ticoş, C. M.

    2015-10-15

    The vertical precession of cylindrical dust particles levitated in the sheath of an rf plasma is experimentally investigated. Typically, the dust particles have two equilibrium positions depending on the orientation of their longitudinal axis: horizontal and vertical. A transition between these two states is induced by rapidly increasing the neutral gas pressure in the plasma chamber. During this transition, the cylindrical dust particles make an angle with the horizontal and rotate about their center of mass. The rotation speed increases as the dust rods aligned with the vertical axis. All dust particles will eventually end up in the vertical state while spinning fast about their longitudinal axis. Dust-dust interaction and the attracting ion wakes are possible mechanisms for inducing the observed dust precession.

  7. Sheath Physics and Boundary Conditions for Edge Plasmas

    SciTech Connect

    Cohen, R H; Ryutov, D D

    2003-09-03

    The boundary conditions of mass, momentum, energy, and charge appropriate for fluid formulations of edge plasmas are surveyed. We re-visit the classic problem of 1-dimensional flow, and note that the ''Bohm sheath criterion'' is requirement of connectivity of the interior plasma with the external world, not the result of termination of the plasma by a wall. We show that the nature of the interior plasma solution is intrinsically different for ion sources that inject above and below the electron sound speed. We survey the appropriate conditions to apply, and resultant fluxes, for a magnetic field obliquely incident on a wall, including the presence of drifts and radial transport. We discuss the consequences of toroidal asymmetries in wall properties, as well as experimental tests of such effects. Finally, we discuss boundary-condition modifications in the case of rapidly varying plasma conditions.

  8. Cerebral malignant nerve sheath tumor, triton tumor variant: case report.

    PubMed

    Bornstein-Quevedo, Leticia; Peralta-Olvera, Fabiola; Marhx-Bracho, Alfonso; Rodríguez-Jurado, Rodolfo; De Leon-Bojorge, Beatriz

    2003-01-01

    A case of a cerebral malignant triton tumor in a 3-year-old boy with a 2-month history of frontal headache and no clinical evidence of neurofibromatosis is reported. The computed tomography (CT) scan showed a large, irregular tumor in the right parietooccipital lobe. A partial surgical resection was performed. Histologically, the tumor was highly cellular and consisted of spindle cells with hyperchromatic and pleomorphic nuclei. Focally, neoplastic cells with rhabdomyoblastic features were found. The immunohistochemical study showed that tumor cells were positive for S-100 protein and CD57, and the rhabdomyoblasts expressed desmin, Myo-D1, and myoglobin. During the postoperative period, a massive intraparenchymal hemorrhage was identified and surgical drainage was performed. The patient worsened and died 10 days after the first surgery. Postmortem study was not authorized. Six cases of cerebral malignant nerve sheath tumor have been described; however, primary intraparenchymal malignant triton tumor has not been previously described.

  9. Nerve sheath myxoma of the dorsal paravertebral space

    PubMed Central

    Malkoc, Melih; Ormeci, Tugrul; Keskinbora, Mert; Yılmaz, Adem; Korkmaz, Ozgur; Tanik, Canan Besleyici

    2014-01-01

    INTRODUCTION Nerve sheath myxomas (NSM) are rare benign soft tissue tumors. The dorsal paravertebral placed NMS diagnosis can be difficult. PRESENTATION OF CASE This article presents clinical, radiological findings and treatment of the NSM of the dorsal paravertebral space in a 32-year-old man presented with a right shoulder and back pain for 4 years. DISCUSSION NSM is a rare and benign tumor and that most often occurs in the skin of the head, neck or upper limbs of younger patients. Rare locations such as intracranial, spinal canal, trunk, lower limb and oral cavity were also reported. The appropriate treatment of NSM is surgical excision. Diagnosis is difficult in an uncommon presentation. CONCLUSION Although the most presented case of NMS are dermal tumors, it may also be found extremely rare locations. We conclude that, the definitive treatment of NSM is surgical excision with safe margins even when it is possible. PMID:25462051

  10. Quantification of rice sheath blight progression caused by Rhizoctonia solani.

    PubMed

    Su'udi, Mukhamad; Park, Jong-Mi; Kang, Woo-Ri; Hwang, Duk-Ju; Kim, Soonok; Ahn, Il-Pyung

    2013-06-01

    Rhizoctonia solani has a wide host range, including almost all cultivated crops and its subgroup anastomosis group (AG)-1 IA causes sheath blight in rice. An accurate measurement of pathogen's biomass is a convincing tool for enumeration of this disease. Mycological characteristics and molecular diagnosis simultaneously supported that all six strains in this study were R. solani AG-1 IA. Heterokaryons between strains Rs40104, Rs40105, and Rs45811 were stable and viable, whereas Rs40103 and Rs40106 did not form viable fused cells, except for the combination of Rs40106 and Rs40104. A primer pair was highly specific to RsAROM gene of R. solani strains and the amplified fragment exists as double copies within fungal genome. The relationship between crossing point (CP) values and the amount of fungal DNA was reliable (R (2) >0.99). Based on these results, we determined R. solani's proliferation within infected stems through real time PCR using a primer pair and a Taqman probe specific to the RsAROM gene. The amount of fungal DNA within the 250 ng of tissue DNA from rice cv. Dongjin infected with Rs40104, Rs40105, and Rs45811 were 7.436, 5.830, and 5.085 ng, respectively. In contrast, the fungal DNAs within the stems inoculated with Rs40103 and Rs40106 were 0.091 and 0.842 ng. The sheath blight symptom progression approximately coincided with the amount of fungal DNA within the symptoms. In summary, our quantitative evaluation method provided reliable and objective results reflecting the amount of fungal biomass within the infected tissues and would be useful for evaluation of resistance germplasm or fungicides and estimation of inoculum potential.

  11. The sheath structure around a negatively charged rocket payload

    SciTech Connect

    Neubert, T.; Gilchrist, B.E.; Banks, P.M.; Williamson, P.R. ); Mandell, M.J.; Katz, I. ); Sasaki, S.; Oyama, K.I. ); Raitt, W.J.; Meyers, N.B. )

    1990-05-01

    The sheath structure around a rocket payload charged up to 460 V negative relative to the ambient ionospheric plasma is investigated experimentally and by computer simulations. In one of the experimental modes, the voltage between the payloads was increased linearly from 0 to 460 V in 2.5 s. In this case the tethered mother/daughter functioned as a double probe, the negative probe (mother) reaching large negative potentials, while the positive probe (daughter) stayed close to the ambient plasma potential. A floating probe array was mounted on the mother with probes located, 25, 50, 75, and 100 cm from the rocket surface. The internal impedance of the array was smaller than the probe/plasma impedance, which influenced the potential measurements. However, the measurements contain signatures, which the authors interpret as resulting from the outward expansion of the ion sheath with increasing negative mother potential. This conclusion is substantiated by NASCAP/LEO computer simulations of space charge limited flow. At high potentials, the observed ion current flowing to the mother increased more strongly with bias potential than found from the simulations. It is suggested that the enhancement of the current is generated by secondary electrons emitted by the ions bombarding the payload skin. The effects of the motion of the mother (540-580 m/s) and of the ambient magnetic field have been assessed by the code. It was estimated that the ion current to the mother was increased by 20% relative to a stationary payload, while the incorporation of a magnetic field had no practical influence on the simulation results.

  12. Analytic model of near-field radio-frequency sheaths. I. Tenuous plasma limit

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.

    2009-02-01

    An analytic model is derived for electromagnetic radio-frequency (rf) wave propagation in a waveguide filled by a tenuous plasma with a slightly tilted equilibrium magnetic field B, i.e., by=By/B≪1. The calculation includes the self-consistent coupling between the rf fields and the sheaths at the sheath-plasma interface and can be used to describe antenna sheath formation in the ion cyclotron range of frequencies. The sheaths are treated as thin vacuum regions separating the plasma and metal wall. It is shown that (i) the launched fast wave is coupled parasitically to the slow wave by the magnetic field structure when by≠0 and by the sheath boundary condition, (ii) the sheath voltage Vsh is dependent on the wave parity (the "antenna phasing"), and (iii) integrating the vacuum rf fields, Vvac=-∫dzE∥(vac), gives an overestimate of the sheath voltage. An expression for the self-consistent Vsh including plasma effects and satisfying the Child-Langmuir law is obtained.

  13. The new digital flexible ureteroscopes: 'size does matter'--increased ureteric access sheath use!

    PubMed

    Bach, C; Nesar, S; Kumar, P; Goyal, A; Kachrilas, S; Papatsoris, A; Masood, J; Buchholz, N

    2012-01-01

    To evaluate whether the use of sheaths to access the ureter has increased after the introduction of new digital ureterorenoscopes in patients undergoing flexible ureteroscopy. 140 patients with kidney stones were randomised to be scoped with either an old-generation fibre-optic flexible ureteroscope (DUR-8, Elite, ACMI; distal tip diameter = 6.75 Fr) or a new-generation digital LCD flexible ureteroscope (Invisio D-URD flexible ureteroscope; distal tip diameter = 8.7 Fr). We recorded the necessity to use a sheath to access the ureter, sheath-related and postoperative complications, and whether or not a JJ stent was left behind. 157 (80 fibre-optic and 77 digital) ureterorenoscopies were performed. Ureteral access sheaths were used significantly more frequently with digital scopes (p = 0.00174). Two patients in the digital scope group had a small distal ureteric perforation from the introducer sheath compared with none in the fibre-optic scope group. A statistically significant increase in sheath use was observed in the new-generation digital flexible ureteroscopy group. Despite the improvement in image quality, better durability and improved stone clearance, there are some potential drawbacks of these scopes. The increased distal tip diameter can result in increased use of ureteric access sheaths and this may increase morbidity and expense. Copyright © 2012 S. Karger AG, Basel.

  14. Current Sheath Dynamics and its Evolution Studies in Sahand Filippov Type Plasma Focus

    NASA Astrophysics Data System (ADS)

    Mohammadi, M. A.; Sobhanian, S.; Ghomeishi, M.; Ghareshabani, E.; Moslehi-fard, M.; Lee, S.; Rawat, R. S.

    2009-12-01

    One of the most important factors for optimizing the plasma focus device operation is the dynamics of the plasma. In this paper, we investigated the profile and dynamics of the current sheath by measuring the velocity and distribution of current sheath in Sahand as a Filippov type plasma focus device. For this purpose, the discharge is produced in pure neon gas with capacitor bank stored energies in the range of 14-50 kJ. The current sheath is monitored using two sets of magnetic probes, one with four and other with three equi-distant probe coils. These probes, installed in both radial and axial directions near the edge of the interior electrode (anode), are used for monitoring the distributions and dynamics of the current sheath. The maximum current sheath velocities at radial and axial phase are 4 ± 0.13 and 3.51 ± 0.22 (cm/μs) respectively for 0.25 Torr. The decreasing of CS velocities in going move away from anode surface is one of the our results in this paper. In this paper we conclude that the current sheath velocity at radial phase in Sahand is greater than axial phase. The effect of the neon working gas pressure and working voltage on the current sheath dynamics and its spatial evolution is investigated and presented.

  15. Fibrin sheath and its relation to subsequent events after tunneled dialysis catheter exchange.

    PubMed

    Shanaah, Almothana; Brier, Michael; Dwyer, Amy

    2013-01-01

    The use of tunneled catheters (TDC) for chronic hemodialysis is frequent and often fails due to fibrin or thrombus and infection. We hypothesized that the presence of fibrin sheath in TDC increases the risk for subsequent catheter malfunction and infection. We did a retrospective review of TDC exchanges and de novo placements from January 2005 to September 2011. Demographic data, information about the catheter procedure, and radiological data were collected. Final outcome analysis included 168 procedure events. Three groups of catheter procedures were identified: catheter exchange without a fibrin sheath (CE), catheter exchange with a treated fibrin sheath (CEF), and de novo catheter placements (DCP). Fibrin sheath incidence was 47%. In the CEF group, there was no statistical difference in the incidence of subsequent infections or dysfunctions (7% and 60%, respectively), when compared with the CE group (9% and 43%, respectively), (p=0.3). Mean time to subsequent dysfunction or infection was similar for CEF and CE (135 vs. 136 days, p-value, 0.98). Fibrin sheaths are common and should be evaluated when performing TDC exchange. If the fibrin sheath is treated, there is no increased incidence in subsequent catheter dysfunction or infection compared with patients without a fibrin sheath. © 2013 Wiley Periodicals, Inc.

  16. Verification of high voltage rf capacitive sheath models with particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Lieberman, Michael; Verboncoeur, John

    2009-10-01

    Collisionless and collisional high voltage rf capacitive sheath models were developed in the late 1980's [1]. Given the external parameters of a single-frequency capacitively coupled discharge, plasma parameters including sheath width, electron and ion temperature, plasma density, power, and ion bombarding energy can be estimated. One-dimensional electrostatic PIC codes XPDP1 [2] and OOPD1 [3] are used to investigate plasma behaviors within rf sheaths and bulk plasma. Electron-neutral collisions only are considered for collisionless sheaths, while ion-neutral collisions are taken into account for collisional sheaths. The collisionless sheath model is verified very well by PIC simulations for the rf current-driven and voltage-driven cases. Results will be reported for collisional sheaths also. [1] M. A. Lieberman, IEEE Trans. Plasma Sci. 16 (1988) 638; 17 (1989) 338 [2] J. P. Verboncoeur, M. V. Alves, V. Vahedi, and C. K. Birdsall, J. Comp. Phys. 104 (1993) 321 [3] J. P. Verboncoeur, A. B. Langdon and N. T. Gladd, Comp. Phys. Comm. 87 (1995) 199

  17. Mitigating impact of thermal and rectified radio-frequency sheath potentials on edge localized modes

    SciTech Connect

    Gui, B.; Xu, X. Q.; Myra, J. R.; D'Ippolito, D. A.

    2014-11-15

    The mitigating impact of thermal and rectified radio frequency (RF) sheath potentials on the peeling-ballooning modes is studied non-linearly by employing a two-fluid three-field simulation model based on the BOUT++ framework. Additional shear flow and the Kelvin-Helmholtz effect due to the thermal and rectified RF sheath potential are induced. It is found that the shear flow increases the growth rate while the K-H effect decreases the growth rate slightly when there is a density gradient, but the energy loss of these cases is suppressed in the nonlinear phase. The stronger external electrostatic field due to the sheaths has a more significant effect on the energy loss suppression. From this study, it is found the growth rate in the linear phase mainly determines the onset of edge-localized modes, while the mode spectrum width in the nonlinear phase has an important impact on the turbulent transport. The wider mode spectrum leads to weaker turbulent transport and results in a smaller energy loss. Due to the thermal sheath and rectified RF sheath potential in the scrape-off-layer, the modified shear flow tears apart the peeling-ballooning filament and makes the mode spectrum wider, resulting in less energy loss. The perturbed electric potential and the parallel current near the sheath region is also suppressed locally due to the sheath boundary condition.

  18. Effect of electron reflection on magnetized plasma sheath in an oblique magnetic field

    SciTech Connect

    Wang, Ting-Ting; Ma, J. X. Wei, Zi-An

    2015-09-15

    Magnetized plasma sheaths in an oblique magnetic field were extensively investigated by conventionally assuming Boltzmann relation for electron density. This article presents the study of the magnetized sheath without using the Boltzmann relation but by considering the electron reflection along the magnetic field lines caused by the negative sheath potential. A generalized Bohm criterion is analytically derived, and sheath profiles are numerically obtained, which are compared with the results of the conventional model. The results show that the ion Mach number at the sheath edge normal to the wall has a strong dependence on the wall potential, which differs significantly from the conventional model in which the Mach number is independent of the wall potential. The floating wall potential is lower in the present model than that in the conventional model. Furthermore, the sheath profiles are appreciably narrower in the present model when the wall bias is low, but approach the result of the conventional model when the wall bias is high. The sheath thickness decreases with the increase of ion-to-electron temperature ratio and magnetic field strength but has a complex relationship with the angle of the magnetic field.

  19. Considerations in the surgical use of the flexor sheath and pulley system.

    PubMed

    Lowrie, A G; Lees, V C

    2014-01-01

    The use of the digital flexor sheath to reconstruct damaged structures in the fingers is an intriguing but under-investigated subject. The sheath is anchored firmly to the phalanges and palmar plates and has well-vascularized outer and synovial inner layers. The middle layer is strong and fibrous and not all of it is required for its main biomechanical function of maintaining the moment arm of the flexor tendons. These characteristics have led to several descriptions of different reconstructive uses. In sheath reconstruction, flaps can be used to repair damaged A2 and A4 pulleys. As an anchor, the sheath is useful for tenodeses and tendon transfers. It has been used in the correction of ulnar claw and swan neck deformities. In ligament reconstruction, the A1 pulley has been used to reconstruct the transverse intermetacarpal ligament in cleft hand and ray amputations. The sheath has also been used to cover tendon repairs and periosteal defects with the aim of decreasing adhesions. There is potential for further use of the flexor sheath in reconstructive surgery. The digital flexor sheath can be used to restore various finger functions providing its physiological roles are recognized and preserved. This review considers the different techniques described and their potential uses.

  20. Starch Metabolism in the Leaf Sheaths and Culm of Rice 1

    PubMed Central

    Perez, Consuelo M.; Palmiano, Evelyn P.; Baun, Lyda C.; Juliano, Bienvenido O.

    1971-01-01

    The levels of starch and dextrin, free sugars, soluble protein, and enzymes involved in starch metabolism—α-amylase, β-amylase, phosphorylase, Q-enzyme, R-enzyme, and ADP-glucose starch synthetases—were assayed in the leaf sheaths and culm of the rice plant (Oryza sativa L., variety IR8) during growth. Starch accumulation in the leaf sheaths reached a maximum 10 to 11 weeks after transplanting, the time of development of the rice panicle. Maximal concentration of free sugars occurred earlier. Starch and sugars in the leaf sheaths and culm decreased rapidly during grain development. During starch accumulation, the starch granules of the leaf sheaths increased slightly in size and its gelatinization temperature decreased. The molecular size of amylose and amylopectin and amylose content of the starch were similar in both culm and leaf sheaths. Changes in the level of soluble protein paralleled changes in starch level in the leaf sheaths. Among the enzymes, only synthetase bound to the starch granule paralleled the level of starch in the leaf sheaths and in the culm. ADP-glucose, but not UDP-glucose, was utilized as a glucosyl donor by these starch synthetases. Zymograms of these extracts showed only one α-amylase band, one β-amylase band, two phosphorylase bands, and one Q-enzyme band. PMID:16657631

  1. Sheath structure in plasmas with nonextensively distributed electrons and thermal ions

    SciTech Connect

    Hatami, M. M.

    2015-02-15

    Sheath region of an electropositive plasma consisting of q-nonextensive electrons and singly charged positive ions with finite temperature is modeled. Using Sagdeev's pseudo potential technique to derive the modified sheath formation criterion, it is shown that the velocity of ions at the sheath edge is directly proportional to the ion temperatures and inversely proportional to the degree of nonextensivity of electrons (q-parameter). Using the modified Bohm criterion, effect of degree of nonextensivity of electrons and temperature of positive ions on the characteristics of the sheath region are investigated numerically. It is shown that an increase in the ion temperature gives rise to an increase in the electrostatic potential and the velocity of ions in the sheath regardless of the value of q. Furthermore, it is seen that the sheath width and the density distribution of the charged particles decrease by increasing the temperature of positive ions. In addition, it is found that the positive ion temperature is less effective on the sheath structure for higher values of the q-parameter. Finally, the results obtained for a thermal plasma with nonextensively distributed electrons are compared with the results of a cold plasma with nonextensive electrons and an extensive (Maxwellian) plasma with thermal ions.

  2. Features of the photosynthetic tissue in the sheaths of rice (Oryza sativa L.)

    NASA Astrophysics Data System (ADS)

    Guo, Zhao Wu; He, Qiang; Feng, Deng Hua

    The photosynthesis of rice sheath plays a significant role to furnish rice yield, and it is accounted for 10 to 20% of the final yield. But, limited studies have been done to address this phenomenon and to characterize the features of the photosynthetic tissue in rice sheath. In this paper, a super hybrid rice and a hybrid rice were studied as the experimental materials, and the characteristics of the photosynthetic tissue in rice sheaths were examined by microscopic and super-microscopic observation. The results showed that the photosynthetic tissue of rice sheath was rich in the intact mesophyllous cells full of chloroplasts, grana and thylakoids, which were much the same as those of rice blade. The stomatal density in the outer epidermises of the sheaths was comparable to those in the up- and down-epidermises of the blades. The mesophyllous cells in the sheaths were also rich in chlorophylls, and had the net photosynthetic rate (Pn). Therefore, rice sheath was also full of the intact photosynthetic apparatus similar to those in rice blade, and had capabilities of photosynthesis.

  3. Soil sheaths, photosynthate distribution to roots, and rhizosphere water relations for Opuntia ficus-indica

    SciTech Connect

    Huang, B.; North, G.B.; Nobel, P.S. )

    1993-09-01

    Soil sheaths incorporating aggregated soil particles surround young roots of many species, but the effects of such sheaths on water movement between roots and the soil are largely unknown. The quantity and location of root exudates associated with soil sheath along the entire length of its young roots, except within 1.4 cm of the tip. The soil sheaths, which average 0.7 mm in thickness, were composed of soil particles and root hairs, both of which were covered with exuded mucilaginous material. As determined with a [sup 14]C pulse-labeling technique, 2% of newly fixed [sup 14]C-photosynthate was translocated into the roots at 3d, 6% at 9 d, and 8% at 15 d after labeling. The fraction of insoluble [sup 14]C in the roots increased twofold from 3 d to 15 d. Over the same time period, 6%-9% of the [sup 14]C translocated to the roots was exuded into the soil. The soluble [sup 14]C compounds exuded into the soil were greater in the 3-cm segment at the root tip than elsewhere along the root, whereas mucilage was exuded relatively uniformly along roots 15 cm in length. The volumetric efflux of water increase for both sheathed and unsheathed roots as the soil water potential decreased form -0.1 MPa to -1.0 MPa. The efflux rate was greater for unsheathed roots than for sheathed roots, which were more turgid and had a higher water potential, especially at lower soil water potentials. During drying, soil particles in the sheaths aggregate more tightly, making the sheaths less permeable to water and possibly creating air gaps. The soil sheaths of O. ficus-indica thus reduce water loss from the roots to a drying soil. 34 refs., 6 figs., 1 tab.

  4. Dust charging and charge fluctuations in a weakly collisional radio-frequency sheath at low pressure

    SciTech Connect

    Piel, Alexander Schmidt, Christian

    2015-05-15

    Models for the charging of dust particles in the bulk plasma and in the sheath region are discussed. A new model is proposed that describes collision-enhanced ion currents in the sheath. The collisions result in a substantial reduction of the negative charge of the dust. Experimental data for the dust charge in the sheath can be described by this model when a Bi-Maxwellian electron distribution is taken into account. Expressions for the dust charging rate for all considered models are presented and their influence on the rise of the kinetic dust temperature is discussed.

  5. Peripheral Nerve Sheath Tumor of the Vagus Nerve in a Dog.

    PubMed

    Yap, Fui; Pratschke, Kathryn

    2016-01-01

    A peripheral nerve sheath tumor was diagnosed in a female, neutered Labrador retriever with a 6 mo history of coughing, retching, ptyalism, and left-sided Horner's syndrome. Computed tomography scan of the neck revealed a mass lesion between the carotid artery and esophagus in the mid-cervical region. Exploratory surgery was performed and an 18 cm section of thickened vagus nerve was excised. Histopathological findings and immunochemistry staining confirmed a malignant peripheral nerve sheath tumor. The tumor showed microscopic signs of malignancy, but there were no macroscopic signs of local extension or distant metastasis. This report documents a peripheral nerve sheath tumor of rare origin in dogs.

  6. Fluoroscopically-guided micropuncture femoral artery access for large-caliber sheath insertion.

    PubMed

    Cilingiroglu, Mehmet; Feldman, Ted; Salinger, Michael H; Levisay, Justin; Turi, Zoltan G

    2011-04-01

    Over the last decade, significant developments have been made in the treatment of structural heart disease. Some of these techniques require placement of large arterial sheaths for device delivery. Optimal vascular access is essential for successful large-vessel sheath insertion as well as to avoid vascular complications. The critical step for ideal percutaneous vessel entry is single anterior wall-only puncture of the common femoral artery in a location above the femoral bifurcation and below the inguinal ligament. We describe a fluoroscopically-guided micropuncture technique for accurate placement of large-caliber arterial sheaths.

  7. Ion temperature effects on its chaotic behavior in ion-sheath

    NASA Astrophysics Data System (ADS)

    Soleimani-Iraei, M.; Esfandyari-Kalejahi, A.; Sobhanian, S.

    2017-02-01

    Nonlinear dynamical behavior of an ion with finite temperature in a driven plasma ion-sheath has been studied by a numerical solution of fluid equations. Using the concepts of the nonlinear dynamical system theory, the conditions under which the dynamical behavior of the ion becomes chaotic have been investigated. The numerical results have revealed that there is an order-chaos-order transition in the isothermal plasma ion-sheath due to the external oscillating electric field. In the case of an adiabatic ion-sheath, even with a strong external electric field, no chaotic motion has appeared.

  8. Dynamic Sheaths, in the Nick of Time or Past Their Prime?

    PubMed

    Krajcer, Zvonimir; Parekh, Dhaval

    2016-12-01

    Risk factors for vascular complications include a sheath to femoral artery ratio (SFAR) > 1.05, use of sheaths >19 Fr, peripheral artery disease, female gender, and a learning curve. High rates of technical and procedural success were achieved with low rates of major vascular and bleeding complications. However, SFAR > 1.05, gender, diabetes, renal insufficiency, calcification, tortuosity, or aneurysm were not independent risk factors in this study. Despite an SFAR > 1.05 in 23 patients, increased rates of vascular complications were not seen using the SoloPath sheath. These findings may increase the pool of transfemoral TAVI patients.

  9. The Effect of Polarization on the Stability of Current Sheaths in Space Plasma

    NASA Astrophysics Data System (ADS)

    Lyahov, Vladimir; Neshchadim, Vladimir

    2013-04-01

    The procedure of study of the stability of current sheath taking into account the effect of plasma polarization is proposed. The kinetic equation with self-consistent electromagnetic field for perturbation of distribution function is solved. On the basis of this solution the tensor of dielectric permeability of nonelectroneutral sharply-irregular current sheath plasma is calculated and the dispersion equation to study the possible instability modes of this sheath is obtained. Instability of the current sheath of magnetospheric tail with respect to the tearing-perturbations as well as influence of the effect of plasma polarization on the development of tearing instability is investigated. As a result of application of the offered procedure the existence of low-frequency tearing-like modes which essentially differ from the formerly known tiring-perturbations is revealed even for the case of an electroneutral current sheath. The increment of growth of those modes is positive within very wide interval of wave lengths and attains much bigger quantities than it was supposed earlier for the tearing-instability. Due to this polarization effect, the area of existence of those low-frequency tearing-like modes is displaced from the area of strong stationary electric field more close to the magnitoneutral (and electroneutral) plane at the center of symmetry of the current sheath. The problem of structural stability of the nonelectroneutral current sheath is explored. The equilibrium model represents a system of four connected non-linear first-order differential equations and hence it should manifest the property of structural instability - sensitivity to infinitesimal changes of the parameters and initial conditions. The solution for such current sheath is realized only in some areas of 7-dimensional space of model parameters. The phase volume of those areas is small in comparison with the entire phase volume in the interval on which the parameters are defined. The above is

  10. Phase-resolved measurements of ion velocity in a radio-frequency sheath.

    PubMed

    Jacobs, Brett; Gekelman, Walter; Pribyl, Pat; Barnes, Michael

    2010-08-13

    The time-dependent argon-ion velocity distribution function above and within the plasma sheath of an rf-biased substrate has been measured using laser-induced fluorescence in a commercial plasma processing tool. Discharge parameters were such that the 2.2 MHz rf-bias period was on the order of the ion transit time through the sheath (τ{ion}/τ{rf}=0.3). This work embodies the first time-resolved measurement of ion velocity distribution functions within an rf-biased sheath over a large area (30 cm diameter) silicon wafer substrate.

  11. Generation of fast protons in moderate-intensity laser-plasma interaction from rear sheath

    NASA Astrophysics Data System (ADS)

    Tan, Zhi-Xin; Huang, Yong-Sheng; Lan, Xiao-Fei; Lu, Jian-Xin; Duan, Xiao-Jiao; Wang, Lei-Jian; Yang, Da-Wei; Guo, Shi-Lun; Wang, Nai-Yan

    2010-05-01

    Forward fast protons are generated by the moderate-intensity laser-foil interaction. Protons with maximum energy 190 keV are measured by using magnetic spectrometer and CR-39 solid state track detectors along the direction normal to the rear surface. The experimental results are also modeled by the particle-in-cell method, investigating the time-varying electron temperature and the rear sheath field. The temporal and spatial structure of the sheath electrical field, revealed in the simulation, suggests that these protons are accelerated by target normal sheath acceleration (TNSA) mechanism.

  12. Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths.

    PubMed

    Kunoh, Tatsuki; Nagaoka, Noriyuki; McFarlane, Ian R; Tamura, Katsunori; El-Naggar, Mohamed Y; Kunoh, Hitoshi; Takada, Jun

    2016-08-01

    Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales.

  13. Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths

    PubMed Central

    Kunoh, Tatsuki; Nagaoka, Noriyuki; McFarlane, Ian R.; Tamura, Katsunori; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales. PMID:27490579

  14. Some studies on transient behaviours of sheath formation in dusty plasma with the effect of adiabatically heated electrons and ions

    NASA Astrophysics Data System (ADS)

    Das, G. C.

    2017-09-01

    Based on quasipotential analysis, a plasma sheath is studied through the derivation of the Sagdeev potential equation in dusty plasma coexisting with adiabatically heated electrons and ions. Salient features as to the existence of sheaths are shown by solving the Sagdeev potential equation through the Runge-Kutta method, with appropriate consideration of adiabatically heated electrons and ions in the dynamical system. It has been shown that adiabatic heating of plasma sets a limit to the critical dust speed depending on the densities and Mach number, and it is believed that its role is very important to the sheath. One present problem is the contraction of the sheath region whereby dust grains levitated into the sheath lead to a crystallization similar to the formation of nebulons and are compressed to a larger chunk of the dust cloud by shrinking of the sheath. Our overall observations advance knowledge of sheath formation and are expected to be of interest in astroplasmas.

  15. 3D Parylene sheath neural probe for chronic recordings

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Kuo, J. T. W.; Hara, S. A.; Lee, C. D.; Yu, L.; Gutierrez, C. A.; Hoang, T. Q.; Pikov, V.; Meng, E.

    2013-08-01

    Objective. Reliable chronic recordings from implanted neural probes remain a significant challenge; current silicon-based and microwire technologies experience a wide range of biotic and abiotic failure modes contributing to loss of signal quality. Approach. A multi-prong alternative strategy with potential to overcome these hurdles is introduced that combines a novel three dimensional (3D), polymer-based probe structure with coatings. Specifically, the Parylene C sheath-based neural probe is coated with neurotrophic and anti-inflammatory factors loaded onto a Matrigel carrier to encourage the ingrowth of neuronal processes for improved recording quality, reduce the immune response, and promote improved probe integration into brain tissue for reliable, long-term implementation compared to its rigid counterparts. Main results. The 3D sheath structure of the probe was formed by thermal molding of a surface micromachined Parylene C microchannel, with electrode sites lining the interior and exterior regions of the lumen. Electrochemical characterization of the probes via cyclic voltammetry and electrochemical impedance spectroscopy was performed and indicated suitable electrode properties for neural recordings (1 kHz electrical impedance of ∼200 kΩ in vitro). A novel introducer tool for the insertion of the compliant polymer probe into neural tissue was developed and validated both in vitro using agarose gel and in vivo in the rat cerebral cortex. In vivo electrical functionality of the Parylene C-based 3D probes and their suitability for recording the neuronal activity over a 28-day period was demonstrated by maintaining the 1 kHz electrical impedance within a functional range (<400 kΩ) and achieving a reasonably high signal-to-noise ratio for detection of resolvable multi-unit neuronal activity on most recording sites in the probe. Immunohistochemical analysis of the implant site indicated strong correlations between the quality of recorded activity and the

  16. Microgravity-Driven Optic Nerve/Sheath Biomechanics Simulations

    NASA Technical Reports Server (NTRS)

    Ethier, C. R.; Feola, A.; Myers, J. G.; Nelson, E.; Raykin, J.; Samuels, B.

    2016-01-01

    Visual Impairment and Intracranial Pressure (VIIP) syndrome is a concern for long-duration space flight. Current thinking suggests that the ocular changes observed in VIIP syndrome are related to cephalad fluid shifts resulting in altered fluid pressures [1]. In particular, we hypothesize that increased intracranial pressure (ICP) drives connective tissue remodeling of the posterior eye and optic nerve sheath (ONS). We describe here finite element (FE) modeling designed to understand how altered pressures, particularly altered ICP, affect the tissues of the posterior eye and optic nerve sheath (ONS) in VIIP. METHODS: Additional description of the modeling methodology is provided in the companion IWS abstract by Feola et al. In brief, a geometric model of the posterior eye and optic nerve, including the ONS, was created and the effects of fluid pressures on tissue deformations were simulated. We considered three ICP scenarios: an elevated ICP assumed to occur in chronic microgravity, and ICP in the upright and supine positions on earth. Within each scenario we used Latin hypercube sampling (LHS) to consider a range of ICPs, ONH tissue mechanical properties, intraocular pressures (IOPs) and mean arterial pressures (MAPs). The outcome measures were biomechanical strains in the lamina cribrosa, optic nerve and retina; here we focus on peak values of these strains, since elevated strain alters cell phenotype and induce tissue remodeling. In 3D, the strain field can be decomposed into three orthogonal components, denoted as first, second and third principal strains. RESULTS AND CONCLUSIONS: For baseline material properties, increasing ICP from 0 to 20 mmHg significantly changed strains within the posterior eye and ONS (Fig. 1), indicating that elevated ICP affects ocular tissue biomechanics. Notably, strains in the lamina cribrosa and retina became less extreme as ICP increased; however, within the optic nerve, the occurrence of such extreme strains greatly increased as

  17. The structure and development of the starch sheath in pea epicotyls

    NASA Technical Reports Server (NTRS)

    Sack, D. F.

    1985-01-01

    Graviperception in plant stems is thought to occur in endodermal cells differentiated as a starch sheath, but little is known about the ultrastructure of these cells in dicots. The structure of the pea starch sheath was studied with respect to gravity and to development in order to determine whether symplastic or apoplastic blockages exist and to describe any intracellular polarity. Amyloplasts increase in size towards the base of the epicotyl hook but are not consistently sedimented until the cells enter the zone exhibiting gravicurvature below the hook. The starch sheath cells are connected to each other and to cells of the cortex and the stele by plasmodesmata. A casparian strip exists in older endodermal cells but not at the stage that the endodermis is differentiated as a starch sheath. Amyloplasts were frequently observed in apparent contact with endoplasmic reticulum.

  18. Novel flexible Parylene neural probe with 3D sheath structure for enhancing tissue integration.

    PubMed

    Kuo, Jonathan T W; Kim, Brian J; Hara, Seth A; Lee, Curtis D; Gutierrez, Christian A; Hoang, Tuan Q; Meng, Ellis

    2013-02-21

    A Parylene C neural probe with a three dimensional sheath structure was designed, fabricated, and characterized. Multiple platinum (Pt) electrodes for recording neural signals were fabricated on both inner and outer surfaces of the sheath structure. Thermoforming of Parylene was used to create the three dimensional sheath structures from flat surface micromachined microchannels using solid microwires as molds. Benchtop electrochemical characterization was performed on the thin film Pt electrodes using cyclic voltammetry and electrochemical impedance spectroscopy and showed that electrodes possessed low impedances suitable for neuronal recordings. A procedure for implantation of the neural probe was developed and successfully demonstrated in vitro into an agarose brain tissue model. The electrode-lined sheath will be decorated with eluting neurotrophic factors to promote in vivo neural tissue ingrowth post-implantation. These features will enhance tissue integration and improve recording quality towards realizing reliable chronic neural interfaces.

  19. The endomembrane sheath: a key structure for understanding the plant cell?

    NASA Technical Reports Server (NTRS)

    Reuzeau, C.; McNally, J. G.; Pickard, B. G.

    1997-01-01

    Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

  20. Effect of q-nonextensive distribution of electrons on the sheath in dusty plasma

    NASA Astrophysics Data System (ADS)

    Driouch, Ismael; Chatei, Hassan

    2017-01-01

    In this paper, a sheath model has been developed to investigate the characteristics of a magnetised dusty plasma sheath in the presence of a q-nonextensive distribution of electrons. For this, we have established a one-dimensional fluid model. The electrons are considered following the q-nonextensive distribution (i.e. the deflection of the electrons for their Maxwell-Boltzmann distribution); however the ions and dust grains are described by fluid equations. According to multi-fluid equations and some dimensionless variables, the dimensionless equations are obtained and solved numerically. The effect of the nonextensivity q-parameter on the plasma sheath parameters is examined. A significant change is observed in the quantities characterising the sheath when the electrons evolve far away from their thermodynamic equilibrium Maxwellian ( q = 1) assumption.

  1. Temporally resolved ion velocity distribution measurements in a radio-frequency plasma sheath

    SciTech Connect

    Jacobs, B.; Gekelman, W.; Pribyl, P.; Barnes, M.

    2011-05-15

    The ion velocity distribution function (IVDF) above and within a radio-frequency (RF) biased plasma sheath is studied experimentally with a pulsed laser-induced fluorescence diagnostic in an industrial plasma etch tool. Temporally resolved measurements taken at eight different phases of the 2.2 MHz bias waveform show that the ion dynamics vary dramatically throughout the RF cycle (the ratio of the average ion transit time through the sheath to the RF period is {tau}{sub ion}/{tau}{sub RF} = 0.3). The position of the presheath/sheath edge is constant throughout the RF cycle and the time-averaged ion flux is conserved within the sheath region. The characteristic bimodal structure of the time-averaged ion distributions found in previous experiments is observed to arise from the time-dependent ion dynamics, in accord with existing theory. The large temporal variation of the IVDF has implications for the plasma chemistry and etching quality.

  2. Three dimensional space charge model for large high voltage satellites. [plasma sheath

    NASA Technical Reports Server (NTRS)

    Cooks, D.; Parker, L. W.; Mccoy, J. E.

    1980-01-01

    High power solar arrays for satellite power systems with dimensions of kilometers, and with tens of kilovolts distributed over their surface face many plasma interaction problems that must be properly anticipated. In most cases, the effects cannot be adequately modeled without detailed knowledge of the plasma sheath structure and space charge effects. Two computer programs were developed to provide fully self consistent plasma sheath models in three dimensions as a result of efforts to model the experimental plasma sheath studies at NASA/JSC. Preliminary results indicate that for the conditions considered, the Child-Langmuir diode theory can provide a useful estimate of the plasma sheath thickness. The limitations of this conclusion are discussed. Some of the models presented exhibit the strong ion focusing observed in the JSC experiments.

  3. Discontinuous model with semi analytical sheath interface for radio frequency plasma

    NASA Astrophysics Data System (ADS)

    Miyashita, Masaru

    2016-09-01

    Sumitomo Heavy Industries, Ltd. provide many products utilizing plasma. In this study, we focus on the Radio Frequency (RF) plasma source by interior antenna. The plasma source is expected to be high density and low metal contamination. However, the sputtering the antenna cover by high energy ion from sheath voltage still have been problematic. We have developed the new model which can calculate sheath voltage wave form in the RF plasma source for realistic calculation time. This model is discontinuous that electronic fluid equation in plasma connect to usual passion equation in antenna cover and chamber with semi analytical sheath interface. We estimate the sputtering distribution based on calculated sheath voltage waveform by this model, sputtering yield and ion energy distribution function (IEDF) model. The estimated sputtering distribution reproduce the tendency of experimental results.

  4. 30 CFR 77.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Grounding § 77.700 Grounding metallic sheaths, armors... conductors shall be electrically continuous throughout and shall be grounded by methods approved by...

  5. Resonance Cone Interaction With a Self-Consistent Radio-Frequency Sheath

    SciTech Connect

    Myra, J. R.; D'Ippolito, D. A.

    2008-11-07

    We study the propagation of lower-hybrid-type resonance cones in a tenuous magnetized plasma, and, in particular, their interaction with, and reflection from, the plasma sheath near a conducting wall. The sheath is modeled as a vacuum gap whose width is given by the Child-Langmuir law. The application of interest is when the resonance cones are launched (parasitically) by an ion-cyclotron radio-frequency antenna in a typical rf-heated tokamak fusion experiment. We calculate the fraction of launched voltage in the resonance cones that is transmitted to the sheath, and show that it has a sensitive thresholdlike turn on when a critical parameter reaches order unity. Above threshold, the fractional voltage transmitted to the sheath is order unity, leading to strong and potentially deleterious rf-wall interactions in tokamak rf heating experiments. Below threshold, these interactions can be avoided.

  6. Effect of anisotropy of electron velocity distribution function on dynamic characteristics of sheath in Hall thrusters

    SciTech Connect

    Zhang Fengkui; Wu Xiande; Ding Yongjie; Li Hong; Yu Daren

    2011-10-15

    In Hall thrusters, the electron velocity distribution function is not only depleted at high energies, but also strongly anisotropic. With these electrons interacting with the channel wall, the sheath will be changed in its dynamic characteristics. In the present letter, a two dimensional particle-in-cell code is used to simulate these effects in a collisionless plasma slab. The simulated results indicate that the sheath changes from steady regime to temporal oscillation regime when the electron velocity distribution function alters from isotropy to anisotropy. Moreover, the temporal oscillation sheath formed by the anisotropic electrons has a much greater oscillating amplitude and a much smaller average potential drop than that formed by the isotropic electrons has. The anisotropic electrons are also found to lower the critical value of electron temperature needed for the appearance of the spatial oscillation sheath.

  7. The endomembrane sheath: a key structure for understanding the plant cell?

    NASA Technical Reports Server (NTRS)

    Reuzeau, C.; McNally, J. G.; Pickard, B. G.

    1997-01-01

    Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

  8. Magnetized sheath near positively biased wall between two permanent magnetic plates

    SciTech Connect

    Sun, Yan; Wei, Zi-an; Ma, J. X. Jiang, Zheng-qi; Wu, Fei

    2015-06-15

    The characteristics of magnetized electron sheath near a positively biased conducting wall parallel to magnetic field formed between two permanent magnetic plates were experimentally investigated in a double plasma device. The magnetic field strength between the magnetic plates is about 1200 G which is sufficient to magnetize the plasma such that the ion gyroradius is comparable to the electron Debye length. A virtual cathode (or potential dip) structure was found between the electron-rich sheath and bulk plasma. For a given neutral gas pressure, the potential minimum (dip position) remains almost the same for different positive biases on the wall. For a given bias on the wall, however, the electron sheath thickness and the potential drop from the bulk plasma to the dip decrease with the increase of the neutral gas pressure. In addition, the electron sheath and potential dip appear to be wider and deeper in the downstream side of the wall.

  9. 3D RMHD Simulations of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Philip; Nishikawa, Ken-Ichi

    2008-01-01

    We have performed numerical simulations of weakly and strongly magnetized relativistic jets embedded in a weakly and strongly magnetized stationary or mildly relativistic (0.5c) sheath flow using the RAISHIN code. In the numerical simulations a jet with Lorentz factor gamma=2.5 is processed to break the initial equilibrium configuration. Results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized RMHD equations describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized sheath flow. The prediction of increased stability of a weakly-magnetized system with mildly relativistic sheath flow to Kelvin-Helmholtz instabilities and the stabilization of a strongly magnetized system with mildly relativistic sheath flow is confirmed by the numerical simulations.

  10. 3D RMHD Simulations of Magnetized Spine-sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Phillip; Ken-Ichi, Nishikawa

    2008-01-01

    We have performed numerical simulations of weakly and strongly magnetized relativistic jets embedded in a weakly and strongly magnetized stationary or mildly relativistic'(0.5c) sheath flow using the RAISHIN code. In the numerical simulations a jet with Lorentz factor gamma=2.5 is processed to break the initial equilibrium configuration. Results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized RMHD equations describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized sheath flow. The prediction of increased stability of a weakly-magnetized system with mildly relativistic sheath flow to Kelvin-Helmholtz instabilities and the stabilization of a strongly-magnetized system with mildly relativistic sheath flow is confirmed by the numerical simulations.

  11. Enhancing resolution of free-flow zone electrophoresis via a simple sheath-flow sample injection.

    PubMed

    Yang, Ying; Kong, Fan-Zhi; Liu, Ji; Li, Jun-Min; Liu, Xiao-Ping; Li, Guo-Qing; Wang, Ju-Fang; Xiao, Hua; Fan, Liu-Yin; Cao, Cheng-Xi; Li, Shan

    2016-07-01

    In this work, a simple and novel sheath-flow sample injection method (SFSIM) is introduced to reduce the band broadening of free-flow zone electrophoresis separation in newly developed self-balance free-flow electrophoresis instrument. A needle injector was placed in the center of the separation inlet, into which the BGE and sample solution were pumped simultaneously. BGE formed sheath flow outside the sample stream, resulting in less band broadening related to hydrodynamics and electrodynamics. Hemoglobin and C-phycocyanin were successfully separated by the proposed method in contrast to the poor separation of free-flow electrophoresis with the traditional injection method without sheath flow. About 3.75 times resolution enhancement could be achieved by sheath-flow sample injection method.

  12. Antifungal Action of Ginkgo biloba Outer Seedcoat on Rice Sheath blight

    PubMed Central

    Oh, Tae-Seok; Koo, Han-Mo; Yoon, Hei-Ryeo; Jeong, Nam-Su; Kim, Yeong-Jin; Kim, Chang-Ho

    2015-01-01

    From study of antifungal actions on the rice sheath blight by using the extract of Ginkgo biloba outer seedcoats, we found that the extracts of Ginkgo biloba outer seedcoats of all treatment concentrations had inhibited the rice sheath blight. Among them, the most effective concentration was 250 mg/l at which the growth of microbe was 26 mm and even at the packaging test, when sprayed the G. biloba outer seedcoats at the level of 250 mg/l, the damage rate of the rice sheath blight was identified as 13%. As a result investigating the antifungal activity by separating polysaccharides from G. biloba outer seedcoats, it showed that the clear zone of 14 mm or more was formed at the concentration of 250 mg/l or higher. Based on these results, we concluded that the G. biloba outer seedcoat is a natural substance with the antifungal activity on the rice sheath blight. PMID:25774111

  13. A Semianalytical Ion Current Model for Radio Frequency Driven Collisionless Sheaths

    NASA Technical Reports Server (NTRS)

    Bose, Deepak; Govindan, T. R.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2001-01-01

    We propose a semianalytical ion dynamics model for a collisionless radio frequency biased sheath. The model uses bulk plasma conditions and electrode boundary condition to predict ion impact energy distribution and electrical properties of the sheath. The proposed model accounts for ion inertia and ion current modulation at bias frequencies that are of the same order of magnitude as the ion plasma frequency. A relaxation equation for ion current oscillations is derived which is coupled with a damped potential equation in order to model ion inertia effects. We find that inclusion of ion current modulation in the sheath model shows marked improvements in the predictions of sheath electrical properties and ion energy distribution function.

  14. Experimental Studies of Anode Sheath Phenomena in a Hall Thruster Discharge

    SciTech Connect

    L. Dorf; Y. Raitses; N.J. Fisch

    2004-12-17

    Both electron-repelling and electron-attracting anode sheaths in a Hall thruster were characterized by measuring the plasma potential with biased and emissive probes [L. Dorf, Y. Raitses, V. Semenov, and N.J. Fisch, Appl. Phys. Let. 84 (2004) 1070]. In the present work, two-dimensional structures of the plasma potential, electron temperature, and plasma density in the near-anode region of a Hall thruster with clean and dielectrically coated anodes are identified. Possible mechanisms of anode sheath formation in a Hall thruster are analyzed. The path for current closure to the anode appears to be the determining factor in the anode sheath formation process. The main conclusion of this work is that the anode sheath formation in Hall thrusters differs essentially from that in the other gas discharge devices, like a glow discharge or a hollow anode, because the Hall thruster utilizes long electron residence times to ionize rather than high neutral pressures.

  15. Polyacrylonitrile nanofibers prepared using coaxial electrospinning with LiCl solution as sheath fluid

    NASA Astrophysics Data System (ADS)

    Yu, Deng-Guang; Lu, Ping; Branford-White, Christopher; Yang, Jun-He; Wang, Xia

    2011-10-01

    A modified coaxial electrospinning process including an electrolyte solution as sheath fluid was used for preparing high quality polymer nanofibers. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing a coaxial electrospinning containing LiCl in N, N-dimethylacetamide (DMAc) as the sheath fluid. FESEM results demonstrated that the sheath LiCl solutions have a significant influence on the quality of PAN nanofibers. Nanofibers with smaller diameters, smoother surfaces and uniform structures were successfully prepared. The diameters of nanofibers were controlled by adjusting the conductivity of the sheath fluid over a suitable range and this was determined by varying LiCl concentrations. The influence of the effect of LiCl on the formation of PAN fibers is discussed and it is concluded that coaxial electrospinning with electrolyte solutions is a convenient and facile process for achieving high quality polymer nanofibers.

  16. Simulation study of the photoemission effects in an electrostatic plasma sheath containing charged nanoparticles

    NASA Astrophysics Data System (ADS)

    Jalilpour, P.; Foroutan, G.

    2017-06-01

    Numerical simulations of the multi-fluid equations are utilized to investigate the effects of a directed photon flux on the structure of an electrostatic plasma sheath in the presence of nano-sized dust grains. The results revealed that the sheath width decreases with an increase in the photon flux as well as the photoelectric efficiency, and that the effect is prominent at high plasma number densities. With the increase in the incident flux, the absolute dust charge decreases immediately until it changes sign and becomes positive at moderate fluxes and then increases quite slowly. The ion drag is also reduced by the photoemission, while the electric force is enhanced. The net effect is an enhancement of the total force on the dust grains towards the sheath edge, leading to a significantly reduced dust speed and consequently an increased dust number density throughout the sheath.

  17. Acute Carpal Tunnel Syndrome Caused by Diffuse Giant Cell Tumor of Tendon Sheath: A Case Report

    PubMed Central

    Ward, Christina M; Lueck, Nathan E; Steyers, Curtis M

    2007-01-01

    A 46 year old male developed spontaneous acute carpal tunnel syndrome of the right wrist without any antecedent trauma. Surgical exploration revealed hemorrhage secondary to diffuse giant cell tumor of tendon sheath as the underlying cause. PMID:17907439

  18. Nonmetallic rigid-flexible outer sheath with pneumatic shapelocking mechanism and double curvature structure.

    PubMed

    Zuo, Siyang; Masamune, Ken; Kuwana, Kenta; Tomikawa, Morimasa; Ieiri, Satoshi; Ohdaira, Takeshi; Hashizume, Makoto; Dohi, Takeyoshi

    2011-01-01

    Single port access (SPA) surgery is a laparoscopic procedure using only one transumbilical-placed port. Natural orifice transluminal endoscopic surgery (NOTES) offers the possibility of surgery without visible scars. To address the access and stability problems in SPA and NOTES, we developed a device called rigid-flexible outer sheath. This sheath can be switched between flexible and rigid modes by a novel pneumatic shapelocking mechanism, and it has a double curvature structure that enables it to flex in four directions at the distal end and three directions on the rigid-flexible shaft. The insertion part of the prototype is 300 mm long with a 20 mm outer diameter, and the part is equipped with four working channels. In vivo experiments using a swine show that the outer sheath has high potential for solving access and stability problems. We expect that the outer sheath will be useful for SPA and NOTES.

  19. ICME-driven sheath regions deplete the outer radiation belt electrons

    NASA Astrophysics Data System (ADS)

    Hietala, H.; Kilpua, E. K.; Turner, D. L.

    2013-12-01

    It is an outstanding question in space weather and solar wind-magnetosphere interaction studies, why some storms result in an increase of the outer radiation belt electron fluxes, while others deplete them or produce no change. One approach to this problem is to look at differences in the storm drivers. Traditionally drivers have been classified to Stream Interaction Regions (SIRs) and Interplanetary Coronal Mass Ejections (ICMEs). However, an 'ICME event' is a complex structure: The core is a magnetic cloud (MC; a clear flux rope structure). If the mass ejection is fast enough, it can drive a shock in front of it. This leads to the formation of a sheath region between the interplanetary shock and the leading edge of the MC. While both the sheath and the MC feature elevated solar wind speed, their other properties are very different. For instance, the sheath region has typically a much higher dynamic pressure than the magnetic cloud. Moreover, the sheath region has a high power in magnetic field and dynamic pressure Ultra Low Frequency (ULF) range fluctuations, while the MC is characterised by an extremely smooth magnetic field. Magnetic clouds have been recognised as important drivers magnetospheric activity since they can comprise long periods of very large southward Interplanetary Magnetic Field (IMF). Nevertheless, previous studies have shown that sheath regions can also act as storm drivers. In this study, we analyse the effects of ICME-driven sheath regions on the relativistic electron fluxes observed by GOES satellites on the geostationary orbit. We perform a superposed epoch analysis of 31 sheath regions from solar cycle 23. Our results show that the sheaths cause an approximately one order of magnitude decrease in the 24h-averaged electron fluxes. Typically the fluxes also stay below the pre-event level for more than two days. Further analysis reveals that the decrease does not depend on, e.g., whether the sheath interval contains predominantly northward

  20. Fibrin Sheath Angioplasty: A Technique to Prevent Superior Vena Cava Stenosis Secondary to Dialysis Catheters

    PubMed Central

    Hacker, Robert I.; Garcia, Lorena De Marco; Chawla, Ankur; Panetta, Thomas F.

    2012-01-01

    Fibrin sheaths are a heterogeneous matrix of cells and debris that form around catheters and are a known cause of central venous stenosis and catheter failure. A total of 50 cases of central venous catheter fibrin sheath angioplasty (FSA) after catheter removal or exchange are presented. A retrospective review of an outpatient office database identified 70 eligible patients over a 19-month period. After informed consent was obtained, the dialysis catheter exiting the skin was clamped, amputated, and a wire was inserted. The catheter was then removed and a 9-French sheath was inserted into the superior vena cava, a venogram was performed. If a fibrin sheath was present, angioplasty was performed using an 8 × 4 or 10 × 4 balloon along the entire length of the fibrin sheath. A completion venogram was performed to document obliteration of the sheath. During the study, 50 patients were diagnosed with a fibrin sheath, and 43 had no pre-existing central venous stenosis. After FSA, 39 of the 43 patient's (91%) central systems remained patent without the need for subsequent interventions; 3 patients (7%) developed subclavian stenoses requiring repeat angioplasty and stenting; 1 patent (2.3%) developed an occlusion requiring a reintervention. Seven patients with prior central stenosis required multiple angioplasties; five required stenting of their central lesions. Every patient had follow-up fistulograms to document long-term patency. We propose that FSA is a prudent and safe procedure that may help reduce the risk of central venous stenosis from fibrin sheaths due to central venous catheters. PMID:23997555

  1. Prevention and Treatment of Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors

    DTIC Science & Technology

    2016-04-01

    notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does...ABSTRACT The most common cause of death in Neurofibromatosis Type 1 (NF1) patients is malignant peripheral nerve sheath tumor (MPNST). MPNSTs are...expectancy by ten to twenty years. Malignant peripheral nerve sheath tumors (MPNSTs) are the leading cause of death in NF1 patients and typically arise

  2. Receptor Tyrosine Kinases as Targets for Treatment of Peripheral Nerve Sheath Tumors in NF 1 Patients

    DTIC Science & Technology

    2010-03-01

    by interphase cytogenetics (FISH) in malignant peripheral nerve sheath tumor (MPNST) and morphologically similar spindle cell neoplasms . J...Chronic myeloproliferative disorders with rearrangement of the platelet-derived growth factor alpha receptor: a new clinical target for STI571/Glivec...malignant peripheral nerve sheath tumor (MPNST) and morphologically similar spindle cell neoplasms . J Neuropathol Exp Neurol. 2002;61:702–709. 8

  3. Tunneled dialysis catheter exchange with fibrin sheath disruption is not associated with increased rate of bacteremia.

    PubMed

    Valliant, Amanda M; Chaudhry, Muhammad K; Yevzlin, Alexander S; Astor, Brad; Chan, Micah R

    2015-01-01

    Tunneled dialysis catheters are the most common form of vascular access among incident dialysis patients in the United States. Fibrin sheath formation is a frequent cause of late catheter dysfunction requiring an exchange procedure with balloon disruption of the fibrin sheath. It is unknown whether fibrin sheath disruption is associated with increased incidence of bacteremia or catheter failure. We reviewed all tunneled dialysis catheter exchange procedures at the University of Wisconsin between January 2008 and December 2011. The primary outcome was incidence of bacteremia, defined as positive blood cultures within 2 weeks of the procedure. Catheter failure, requiring intervention or replacement, was examined as a secondary outcome. Baseline characteristics examined included diabetic status, gender, race and age. A total of 163 procedures were reviewed; 67 (41.1%) had fibrin sheath disruption and 96 did not. Bacteremia occurred in 4.5% (3/67) of those with and 3.1% (3/97) of those without fibrin sheath disruption (p=0.65). Fibrin sheath disruption was not significantly associated with the risk of catheter failure (adjusted hazard ratio [aHR]=1.34; 95% confidence interval [CI]: 0.87-2.10; p=0.18). Diabetes was associated with greater risk of catheter failure (aHR=1.88; 95% CI: 1.19-2.95; p=0.006), whereas higher age was associated with a lower risk of catheter failure (aHR per 10 years=0.83; 95% CI: 0.72-0.96; p=0.01). This study demonstrates that there is no significant increase in bacteremia and subsequent catheter dysfunction rates after fibrin sheath disruption compared to simple over the wire exchange. These results are encouraging given the large numbers of patients utilizing tunneled catheters for initial hemodialysis access and the known rates of fibrin sheath formation leading to catheter failure.

  4. Fibrin sheath angioplasty: a technique to prevent superior vena cava stenosis secondary to dialysis catheters.

    PubMed

    Hacker, Robert I; Garcia, Lorena De Marco; Chawla, Ankur; Panetta, Thomas F

    2012-09-01

    Fibrin sheaths are a heterogeneous matrix of cells and debris that form around catheters and are a known cause of central venous stenosis and catheter failure. A total of 50 cases of central venous catheter fibrin sheath angioplasty (FSA) after catheter removal or exchange are presented. A retrospective review of an outpatient office database identified 70 eligible patients over a 19-month period. After informed consent was obtained, the dialysis catheter exiting the skin was clamped, amputated, and a wire was inserted. The catheter was then removed and a 9-French sheath was inserted into the superior vena cava, a venogram was performed. If a fibrin sheath was present, angioplasty was performed using an 8 × 4 or 10 × 4 balloon along the entire length of the fibrin sheath. A completion venogram was performed to document obliteration of the sheath. During the study, 50 patients were diagnosed with a fibrin sheath, and 43 had no pre-existing central venous stenosis. After FSA, 39 of the 43 patient's (91%) central systems remained patent without the need for subsequent interventions; 3 patients (7%) developed subclavian stenoses requiring repeat angioplasty and stenting; 1 patent (2.3%) developed an occlusion requiring a reintervention. Seven patients with prior central stenosis required multiple angioplasties; five required stenting of their central lesions. Every patient had follow-up fistulograms to document long-term patency. We propose that FSA is a prudent and safe procedure that may help reduce the risk of central venous stenosis from fibrin sheaths due to central venous catheters.

  5. Highly Compliant Vascular Grafts with Gelatin-Sheathed Coaxially Structured Nanofibers.

    PubMed

    Nagiah, Naveen; Johnson, Richard; Anderson, Roy; Elliott, Winston; Tan, Wei

    2015-12-01

    We have developed three types of materials composed of polyurethane-gelatin, polycaprolactone-gelatin, or polylactic acid-gelatin nanofibers by coaxially electrospinning the hydrophobic core and gelatin sheath with a ratio of 1:5 at fixed concentrations. Results from attenuated total reflection-Fourier transformed infrared spectroscopy demonstrated the gelatin coating around nanofibers in all of the materials. Transmission electron microscopy images further displayed the core-sheath structures showing the core-to-sheath thickness ratio varied greatly with the highest ratio found in polyurethane-gelatin nanofibers. Scanning electron microscopy images revealed similar, uniform fibrous structures in all of the materials, which changed with genipin cross-linking due to interfiber interactions. Thermal analyses revealed varied interactions between the hydrophilic sheath and hydrophobic core among the three materials, which likely caused different core-sheath structures, and thus physicomechanical properties. The addition of gelatin around the hydrophobic polymer and their interactions led to the formation of graft scaffolds with tissue-like viscoelasticity, high compliance, excellent swelling capability, and absence of water permeability while maintaining competent tensile modulus, burst pressure, and suture retention. The hydrogel-like characteristics are advantageous for vascular grafting use, because of the capability of bypassing preclotting prior to implantation, retaining vascular fluid volume, and facilitating molecular transport across the graft wall, as shown by coculturing vascular cells sandwiched over a thick-wall scaffold. Varied core-sheath interactions within scaffolding nanofibers led to differences in graft functional properties such as water swelling ratio, compliance, and supporting growth of cocultured vascular cells. The PCL-gelatin scaffold with thick gelatin-sheathed nanofibers demonstrated a more compliant structure, elastic mechanics, and high

  6. Wall current closure effects on plasma and sheath fluctuations in Hall thrusters

    SciTech Connect

    Frias, Winston Smolyakov, Andrei I.; Kaganovich, Igor D.; Raitses, Yevgeny

    2014-06-15

    The excitation of negative energy, ion sound type modes driven by the E × B drift and the reactive/dissipative response of the wall sheath interface is analyzed for conditions typical in a Hall thruster. Such sheath impedance modes are sensitive to the dielectric properties of the thruster wall material, which therefore may have direct influence (other than via the secondary electron emission) on fluctuations and transport. Our results predict mode frequencies consistent with the frequencies of fluctuations observed experimentally.

  7. Rectus abdominis muscle free flap harvest by laparoscopic sheath-sparing technique.

    PubMed

    Greensmith, A; Januszkiewicz, J; Poole, G

    2000-04-01

    Previous reports of endoscopic rectus abdominis muscle harvest have described techniques that are hampered by the need for anterior rectus sheath division or mechanical devices to maintain the optical cavity. The authors report the first successful clinical case of a laparoscopic sheath-sparing rectus abdominis muscle harvest for free tissue transfer. It offers considerable advantages over the traditional open method and, with the help of an experienced laparoscopic surgeon, it should add little to operative time.

  8. A Rapamycin-Releasing Perivascular Polymeric Sheath Produces Highly Effective Inhibition of Intimal Hyperplasia

    PubMed Central

    Yu, Xaohua; Takayama, Toshio; Goel, Shakti A.; Shi, Xudong; Zhou, Yifan; Kent, K. Craig; Murphy, William L.; Guo, Lian-Wang

    2014-01-01

    Intimal hyperplasia produces restenosis (re-narrowing) of the vessel lumen following vascular intervention. Drugs that inhibit intimal hyperplasia have been developed, however there is currently no clinical method of perivascular drug-delivery to prevent restenosis following open surgical procedures. Here we report a poly(ε-caprolactone) (PCL) sheath that is highly effective in preventing intimal hyperplasia through perivascular delivery of rapamycin. We first screened a series of bioresorbable polymers, i.e., poly(lactide-co-glycolide) (PLGA), poly(lactic acid) (PLLA), PCL, and their blends, to identify desired release kinetics and sheath physical properties. Both PLGA and PLLA sheaths produced minimal (<30%) rapamycin release within 50 days in PBS buffer. In contrast, PCL sheaths exhibited more rapid and near-linear release kinetics, as well as durable integrity (>90 days) as evidenced in both scanning electron microscopy and subcutaneous embedding experiments. Moreover, a PCL sheath deployed around balloon-injured rat carotid arteries was associated with a minimum rate of thrombosis compared to PLGA and PLLA. Morphometric analysis and immunohistochemistry revealed that rapamycin-loaded perivascular PCL sheaths produced pronounced (85%) inhibition of intimal hyperplasia (0.15±0.05 vs 1.01±0.16), without impairment of the luminal endothelium, the vessel’s anti-thrombotic layer. Our data collectively show that a rapamycin-loaded PCL delivery system produces substantial mitigation of neointima, likely due to its favorable physical properties leading to a stable yet flexible perivascular sheath and steady and prolonged release kinetics. Thus, a PCL sheath may provide useful scaffolding for devising effective perivascular drug delivery particularly suited for preventing restenosis following open vascular surgery. PMID:24852098

  9. Effects of an anode sheath on energy and momentum transfer in vacuum arcs

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxing; Zhou, Zhipeng; Tian, Yunbo; Wang, Haoran; Wang, Jianhua; Geng, Yingsan; Liu, Zhiyuan

    2017-07-01

    Anode phenomena under high-current vacuum arcs have a significant impact on the interrupting capacity of vacuum interrupters. However, the vacuum arc energy flux and momentum flux on the anode—which are necessary boundary conditions for simulations—are either set to an imaginary distribution or calculated using simple formulas without considering anode sheath regulatory effects. The objective of this paper is to reveal the anode sheath effects on regulating the energy and momentum transfer from the arc column to the anode surface in vacuum arcs. A particle-in-cell model for the anode sheath is developed. The required input parameters are obtained from a magnetohydrodynamic model for the arc column. From the results, there exists a sheath near the anode with a negative voltage drop. Both the electron density and the ion density significantly decline in the anode sheath region. The kinetic energy of the ions absorbed by the anode consists of directed kinetic energy, random kinetic energy, and sheath acceleration energy. The sheath acceleration energy contribution is the largest, and the random kinetic energy also accounts for a large part that cannot be ignored. The arc pressure on the anode surface is mainly caused by ion impact, and the accelerating effect of the anode sheath on the ions cannot be neglected in pressure calculations. In addition, in the case of an arc current at 15 kA, the input energy and momentum upon the anode surface is not obviously affected by the evaporated atoms at surface temperatures of 1600 K and 2000 K.

  10. Targeting the ECM to Enhance Drug Delivery in Nf1-Associated Nerve Sheath Tumors

    DTIC Science & Technology

    2016-10-01

    AWARD NUMBER: W81XWH-15-1-0114 TITLE: Targeting the ECM to Enhance Drug Delivery in Nf1-Associated Nerve Sheath Tumors PRINCIPAL INVESTIGATOR...14 Sep 2016 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER NF140089 Targeting the ECM to Enhance Drug Delivery in Nf1-Associated Nerve Sheath Tumors 5b...to determine what factors limit delivery of drugs to tumors of the peripheral nerves, namely neurofibromas (NFs) and their derivative, the malignant

  11. Stress/strain characteristics of Cu-alloy sheath MgB 2 superconducting wires

    NASA Astrophysics Data System (ADS)

    Katagiri, Kazumune; Kasaba, Koichi; Shoji, Yoshitaka; Yamakage, Daisuke; Obara, Takeshi; Shimura, Satoshi; Koshizuka, Naoki; Watanabe, Kazuo

    2007-04-01

    The mechanical properties of Cu and Cu-alloy (Cu-Zr, Cu-Be and Cu-Cr) sheath in situ PIT-processed MgB 2 superconducting wires were studied at room temperature (RT) and 4.2 K. The effects of stress/strain on the critical current ( Ic) of the wires have also been studied at 4.2 K and in magnetic fields up to 5 T. Alloying the Cu sheath significantly increased the yield stress of the wires. The 0.5% flow stresses of the Cu-alloy sheath wires were 147-237 MPa, whereas that of Cu was 55 MPa. At RT, the serration in the stress-strain curves corresponding to the multiple cracking was observed around a strain of 0.4% and the curve almost saturated beyond that point. The strain dependence of Ic prior to the critical strain ( ɛirr) was different depending on the magnetic field; being almost constant at 2 T and increased with strain at 5 T. The Ic decreased beyond ɛirr, which was much larger for Cu-alloy sheath wires as compared with Cu sheath wire. The magnitude of ɛirr is due to the difference in the thermal compressive strain in the MgB 2 core, which was relaxed by yielding in the sheath materials. The transverse compression tests revealed that the Ic of the Cu-alloy sheath wire did not degrade up to about 95 MPa, which is also higher than that of Cu sheath wire.

  12. A rapamycin-releasing perivascular polymeric sheath produces highly effective inhibition of intimal hyperplasia.

    PubMed

    Yu, Xiaohua; Takayama, Toshio; Goel, Shakti A; Shi, Xudong; Zhou, Yifan; Kent, K Craig; Murphy, William L; Guo, Lian-Wang

    2014-10-10

    Intimal hyperplasia produces restenosis (re-narrowing) of the vessel lumen following vascular intervention. Drugs that inhibit intimal hyperplasia have been developed, however there is currently no clinical method of perivascular drug-delivery to prevent restenosis following open surgical procedures. Here we report a poly(ε-caprolactone) (PCL) sheath that is highly effective in preventing intimal hyperplasia through perivascular delivery of rapamycin. We first screened a series of bioresorbable polymers, i.e., poly(lactide-co-glycolide) (PLGA), poly(lactic acid) (PLLA), PCL, and their blends, to identify desired release kinetics and sheath physical properties. Both PLGA and PLLA sheaths produced minimal (<30%) rapamycin release within 50days in PBS buffer. In contrast, PCL sheaths exhibited more rapid and near-linear release kinetics, as well as durable integrity (>90days) as evidenced in both scanning electron microscopy and subcutaneous embedding experiments. Moreover, a PCL sheath deployed around balloon-injured rat carotid arteries was associated with a minimum rate of thrombosis compared to PLGA and PLLA. Morphometric analysis and immunohistochemistry revealed that rapamycin-loaded perivascular PCL sheaths produced pronounced (85%) inhibition of intimal hyperplasia (0.15±0.05 vs 1.01±0.16), without impairment of the luminal endothelium, the vessel's anti-thrombotic layer. Our data collectively show that a rapamycin-loaded PCL delivery system produces substantial mitigation of neointima, likely due to its favorable physical properties leading to a stable yet flexible perivascular sheath and steady and prolonged release kinetics. Thus, a PCL sheath may provide useful scaffolding for devising effective perivascular drug delivery particularly suited for preventing restenosis following open vascular surgery.

  13. Evolution of a dust void in a radio-frequency plasma sheath.

    PubMed

    Dahiya, R P; Paeva, G V; Stoffels, W W; Stoffels, E; Kroesen, G M W; Avinash, K; Bhattacharjee, A

    2002-09-16

    The onset and growth of a dust void are investigated in a radio-frequency (rf) sheath of a capacitively coupled argon plasma. A circularly symmetric void emerges and grows with increasing rf power and pressure in the central region of the dust cloud levitating in the sheath. Experimental measurements of the void diameter are compared with the predictions of a simple phenomenological theory, based on a balance of forces on dust grains.

  14. Optic Nerve Sheath Diameter Increase on Ascent to High Altitude: Correlation With Acute Mountain Sickness.

    PubMed

    Kanaan, Nicholas C; Lipman, Grant S; Constance, Benjamin B; Holck, Peter S; Preuss, James F; Williams, Sarah R

    2015-09-01

    Elevated optic nerve sheath diameter on sonography is known to correlate with increased intracranial pressure and is observed in acute mountain sickness. This study aimed to determine whether optic nerve sheath diameter changes on ascent to high altitude are associated with acute mountain sickness incidence. Eighty-six healthy adults enrolled at 1240 m (4100 ft), drove to 3545 m (11,700 ft) and then hiked to and slept at 3810 m (12,500 ft). Lake Louise Questionnaire scores and optic nerve sheath diameter measurements were taken before, the evening of, and the morning after ascent. The incidence of acute mountain sickness was 55.8%, with a mean Lake Louise Questionnaire score ± SD of 3.81 ± 2.5. The mean maximum optic nerve sheath diameter increased on ascent from 5.58 ± 0.79 to 6.13 ± 0.73 mm, a difference of 0.91 ± 0.55 mm (P = .09). Optic nerve sheath diameter increased at high altitude regardless of acute mountain sickness diagnosis; however, compared to baseline values, we observed a significant increase in diameter only in those with a diagnosis of acute mountain sickness (0.57 ± 0.77 versus 0.21 ± 0.76 mm; P = .04). This change from baseline, or Δ optic nerve sheath diameter, was associated with twice the odds of developing acute mountain sickness (95% confidence interval, 1.08-3.93). The mean optic nerve sheath diameter increased on ascent to high altitude compared to baseline values, but not to a statistically significant degree. The magnitude of the observed Δ optic nerve sheath diameter was positively associated with acute mountain sickness diagnosis. No such significant association was found between acute mountain sickness and diameter elevation above standard cutoff values, limiting the utility of sonography as a diagnostic tool. © 2015 by the American Institute of Ultrasound in Medicine.

  15. Giant cell tumor of the flexor hallucis longus tendon sheath: a case study.

    PubMed

    Findling, Jeff; Lascola, Natalie K; Groner, Thomas W

    2011-01-01

    Giant cell tumor of tendon sheath is infrequently documented in the foot and even less near the ankle. This case report involves such a tumor of the flexor hallucis longus tendon presenting at the posterior ankle. Diagnosis was aided by magnetic resonance imaging, and treatment consisted of complete surgical excision. Pathologic examination verified the diagnosis of giant cell tumor of tendon sheath, and follow-up magnetic resonance imaging revealed no remnants or recurrence of tumor 1 year after surgery.

  16. Exportability of the mitochondrial oxidative phosphorylation machinery into myelin sheath.

    PubMed

    Morelli, Alessandro; Ravera, Silvia; Calzia, Daniela; Panfoli, Isabella

    2011-01-01

    White matter comprises over half of the brain, and its role in axonal survival is being reconsidered, consistently with the observation that axonal degeneration follows demyelination. The recent evidence of an extra-mitochondrial aerobic ATP production in isolated myelin vesicles, thanks to the expression therein of the mitochondrial Oxydative Phosphorylation (OXPHOS) machinery, stands in for myelin playing a functional bioenergetic role in ATP supply for the axon. The observation that subunits of the OXPHOS encoded by the mitochondrial genome are expressed in myelin, suggests that they can be the same as those of the inner mitochondrial membrane. This would mean that the OXPHOS is exportable. Here the hypothesis is exposed that the mitochondrion is the unique site of the assembly of the OXPHOS, so that this is exported to those sub cellular districts displaying high energy demand, such as myelin sheath. There the OXPHOS would display a higher efficiency in oxidative ATP production than inside the mitochondrion itself In this respect, the role of the glia in the nervous conduction is shed new light and the oligodendrocyte mitochondrial OXPHOS are hypothesized to be delivered to nascent myelin.

  17. Evolution and Development of Hertwig’s Epithelial Root Sheath

    PubMed Central

    Luan, Xianghong; Ito, Yoshihiro; Diekwisch, Thomas G.H.

    2009-01-01

    Periodontal regeneration and tissue engineering has re-awakened interest in the role of Hertwig’s Epithelial Root Sheath (HERS), an epithelial tissue layer first discovered in amphibians more than a century ago. Using developmental, evolutionary, and cell biological approaches we have therefore performed a careful analysis of the role of HERS in root formation and compared our data with clinical findings. Our developmental studies revealed HERS as a transient structure assembled in the early period of root formation and elongation and subsequently fenestrated and reduced to epithelial rests of Malassez (ERM). Our comparative evolutionary studies indicated that HERS fenestration was closely associated with the presence of a periodontal ligament and a gomphosis-type attachment apparatus in crocodilians and mammals. Based on these studies, we are proposing that HERS plays an important role in the regulation and maintenance of periodontal ligament space and function. Additional support for this hypothesis was rendered by our meta-analysis of recent clinical reports related to HERS function. PMID:16450392

  18. Bioactive Sheath/Core nanofibers containing olive leaf extract.

    PubMed

    Doğan, Gamze; Başal, Güldemet; Bayraktar, Oğuz; Özyildiz, Figen; Uzel, Ataç; Erdoğan, İpek

    2016-01-01

    This study aimed at producing silk fibroin (SF)/hyaluronic acid (HA) and olive leaf extract (OLE) nanofibers with sheath/core morphology by coaxial electrospinning method, determining their antimicrobial properties, and examining release profiles of OLE from these coaxial nanofibers. Optimum electrospinning process and solution parameters were determined to obtain uniform and bead-free coaxial nanofibers. Scanning electron microscopy and transmission electron microscopy (TEM) were used to characterize the morphology of the nanofibers. The antimicrobial activities of nanofibers were tested according to AATCC test method 100. Total phenolic content and total antioxidant activity were tested using in vitro batch release system. The quality and quantity of released components of OLE were determined by high-performance liquid chromatography. The changes in nanofibers were examined by Fourier-transform infrared spectroscopy. Uniform and bead-free nanofibers were produced successfully. TEM images confirmed the coaxial structure. OLE-loaded nanofibers demonstrated almost perfect antibacterial activities against both of gram-negative and gram-positive bacteria. Antifungal activity against C. albicans was rather poor. After a release period of 1 month, it was observed that ∼70-95% of the OLE was released from nanofibers and it was still bioactive. Overall results indicate that the resultant shell/core nanofibers have a great potential to be used as biomaterials. © 2015 Wiley Periodicals, Inc.

  19. Target normal sheath acceleration analytical modeling, comparative study and developments

    SciTech Connect

    Perego, C.; Batani, D.; Zani, A.; Passoni, M.

    2012-02-15

    Ultra-intense laser interaction with solid targets appears to be an extremely promising technique to accelerate ions up to several MeV, producing beams that exhibit interesting properties for many foreseen applications. Nowadays, most of all the published experimental results can be theoretically explained in the framework of the target normal sheath acceleration (TNSA) mechanism proposed by Wilks et al. [Phys. Plasmas 8(2), 542 (2001)]. As an alternative to numerical simulation various analytical or semi-analytical TNSA models have been published in the latest years, each of them trying to provide predictions for some of the ion beam features, given the initial laser and target parameters. However, the problem of developing a reliable model for the TNSA process is still open, which is why the purpose of this work is to enlighten the present situation of TNSA modeling and experimental results, by means of a quantitative comparison between measurements and theoretical predictions of the maximum ion energy. Moreover, in the light of such an analysis, some indications for the future development of the model proposed by Passoni and Lontano [Phys. Plasmas 13(4), 042102 (2006)] are then presented.

  20. Temperature response of bundle-sheath conductance in maize leaves

    PubMed Central

    Yin, Xinyou; van der Putten, Peter E.L.; Driever, Steven M.; Struik, Paul C.

    2016-01-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g bs responds to temperature. We investigated the temperature response of g bs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5–39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (g m). The estimates of g bs varied greatly with leaf temperature. The temperature response of g bs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of g m had only a slight impact on the temperature response of g bs. In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species. PMID:26969744

  1. Application of Spray Foam Insulation Under Plywood and Oriented Strand Board Roof Sheathing

    SciTech Connect

    Grin, A.; Smegal, J.; Lstiburek, J.

    2013-10-01

    Unvented roof strategies with open cell and closed cell spray polyurethane foam insulation sprayed to the underside of roof sheathing have been used since the mid-1990's to provide durable and efficient building enclosures. However, there have been isolated moisture related incidents reported anecdotally that raise potential concerns about the overall hygrothermal performance of these systems. This project involved hygrothermal modeling of a range of rainwater leakage and field evaluations of in-service residential roofs using spray foam insulation. All of the roof assemblies modeled exhibited drying capacity to handle minor rainwater leakage. All field evaluation locations of in-service residential roofs had moisture contents well within the safe range for wood-based sheathing. Explorations of eleven in-service roof systems were completed. The exploration involved taking a sample of spray foam from the underside of the roof sheathing, exposing the sheathing, then taking a moisture content reading. All locations had moisture contents well within the safe range for wood-based sheathing. One full-roof failure was reviewed, as an industry partner was involved with replacing structurally failed roof sheathing. In this case the manufacturer's investigation report concluded that the spray foam was installed on wet OSB based on the observation that the spray foam did not adhere well to the substrate and the pore structure of the closed cell spray foam at the ccSPF/OSB interface was indicative of a wet substrate.

  2. The magnetized sheath of a dusty plasma with nanosize dust grains

    SciTech Connect

    Mehdipour, H.; Foroutan, G.

    2010-08-15

    The magnetized sheath of a dusty plasma is investigated via numerical simulations of stationary multifluid equations by taking into account the electric, magnetic, gravitational, ion drag, neutral drag, and thermophoretic forces. Dependence of the sheath properties on the characteristics of the magnetic field and plasma parameters is explored. The sheath dynamics is mainly governed by the electric and ion drag forces and the effect of gravitation is negligible. The sheath demonstrates a nonmonotonic behavior against variations of the magnetic intensity and its angle of incidence. The sheath thickness and the maximum of dust density distribution decrease with increasing the ion to electron density ratio at the sheath edge, but increase with growing electron temperature and the positive temperature gradient of the neutrals. The effects of ion drag are similar to those of the gravitational force as both of them accelerate the dust to the wall. By a suitable configuration of the temperature gradient in the neutral gas, thermophoretic force can be utilized to deposit the building units of nanostructures on a substrate or remove any unwanted contaminant from its neighborhood.

  3. Study of Current Sheath Velocity and Its Distribution Using Tridimensional Magnetic Probe in Sahand Plasma Focus

    NASA Astrophysics Data System (ADS)

    A. Mohammadi, M.; Hedyeh, S.

    2015-05-01

    The current sheath velocity in 0.25 Torr gas pressure of Filippov type plasma focus is studied experimentally. By using two tridimensional magnetic probes on top of the anode surface, the current sheath velocity is measured for argon, oxygen and nitrogen. Additionally, the effect of charging voltage on the current sheath velocity is studied in both axial and radial phases. We found that, the maximum current sheath velocities at both radial and axial phases are respectively 4.33 ± 0.28 (cm/μs) and 3.92 ± 0.75 (cm/μs) with argon as the working gas at 17 kV. Also, the minimum values of current sheath velocity are 1.48 ± 0.15 (cm/μs) at the radial phase and 1.14 ± 0.09 (cm/μs) at the axial phase with oxygen at 12 kV. The current sheath velocity at the radial phase is higher than that at the axial phase for all gases and voltages. In this study, variation of the full width half maximum (FWHM) of magnetic probe signals with voltage is investigated for different gases at radial and axial phases.

  4. Bucket and straw technique to facilitate passage of a ventriculoperitoneal shunt through the distal tunneling sheath.

    PubMed

    Downes, Angela E; Vandergrift, William A; Beckman, Joshua M; Truong, Devon; Tuite, Gerald F

    2014-12-01

    Placement of a ventriculoperitoneal shunt (VPS) is a procedure comprising many small steps. Difficulties and delays can arise when passing the distal shunt tubing down the distal tunneling sheath during surgery. The authors of this report describe a simple technique for quickly passing the distal catheter of a VPS through the tunneler sheath, whereby the sheath is used as a fluid tube to allow the distal catheter to be drawn through the fluid tube under suction pressure. The plastic sheath that surrounds the shunt tunneler device is used as a fluid tube, or "straw," with the proximal aperture submerged into a bucket of sterile irrigation liquid containing the distal catheter. Suction pressure is placed against the distal aperture of the tunneler, and the shunt catheter is quickly drawn through the sheath. No special equipment is required. In time trials, the bucket and straw technique took an average of 0.43 seconds, whereas traditional passage methods took 32.3 seconds. The "bucket and straw" method for passing distal shunt tubing through the tunneler sheath is a technique that increases surgical efficiency and reduces manual contact with shunt hardware.

  5. Two-Dimensional Fluid Simulation of Collisional Plasma Sheath over rf Powered Electrode with Cylindrical Hole

    NASA Astrophysics Data System (ADS)

    Hou, Lujing; Wang, Younian; Z, L. Miskvic

    2004-08-01

    The characteristics of collisional radio-frequency (rf) sheath dynamics over an electrode with a cylindrical hole is simulated by means of a self-consistent model which consists of two-dimensional time-dependent fluid equations coupled with Poisson equation. In addition, an equivalent-circuit model is coupled to the fluid equations in order to self-consistently determine relationship between the instantaneous potential at the rf-biased electrode and the sheath thickness. Two-dimensional profiles of the potential, the ion fluid velocity, and the distributions of the ion and electron densities within the sheath are computed under various discharge conditions, such as the discharge powers and the gas pressures. The results show that the existence of the cylindrical hole on the electrode significantly affects the sheath structure and generates a potential trap in the horizontal direction, which is particularly strong when the sheath thickness is comparable to the depth of the hole. Moreover, it is found that the collisional effects have a significant influence on the sheath characteristics.

  6. Movement and structure of mitochondria in oligodendrocytes and their myelin sheaths.

    PubMed

    Rinholm, Johanne E; Vervaeke, Koen; Tadross, Michael R; Tkachuk, Ariana N; Kopek, Benjamin G; Brown, Timothy A; Bergersen, Linda H; Clayton, David A

    2016-05-01

    Mitochondria play several crucial roles in the life of oligodendrocytes. During development of the myelin sheath they are essential providers of carbon skeletons and energy for lipid synthesis. During normal brain function their consumption of pyruvate will be a key determinant of how much lactate is available for oligodendrocytes to export to power axonal function. Finally, during calcium-overload induced pathology, as occurs in ischemia, mitochondria may buffer calcium or induce apoptosis. Despite their important functions, very little is known of the properties of oligodendrocyte mitochondria, and mitochondria have never been observed in the myelin sheaths. We have now used targeted expression of fluorescent mitochondrial markers to characterize the location and movement of mitochondria within oligodendrocytes. We show for the first time that mitochondria are able to enter and move within the myelin sheath. Within the myelin sheath the highest number of mitochondria was in the cytoplasmic ridges along the sheath. Mitochondria moved more slowly than in neurons and, in contrast to their behavior in neurons and astrocytes, their movement was increased rather than inhibited by glutamate activating NMDA receptors. By electron microscopy we show that myelin sheath mitochondria have a low surface area of cristae, which suggests a low ATP production. These data specify fundamental properties of the oxidative phosphorylation system in oligodendrocytes, the glial cells that enhance cognition by speeding action potential propagation and provide metabolic support to axons.

  7. Bit error rate performance of free-space optical link under effect of plasma sheath turbulence

    NASA Astrophysics Data System (ADS)

    Li, Jiangting; Yang, Shaofei; Guo, Lixin; Cheng, Mingjian; Gong, Teng

    2017-08-01

    Based on the power spectrum of the refractive-index fluctuation in the plasma sheath turbulence, the expressions for wave structure functions and scintillation index of optical wave propagating in a turbulent plasma sheath are derived. The effect of the turbulence microstructure on the propagation characteristics of optical waves are simulated and analyzed. Finally, the bit error performance of a free-space optical (FSO) link is investigated under the effect of plasma sheath turbulence. The results indicate that the spherical waves have a better communication performance in the FSO link. In addition, a greater variance of the refractive index fluctuation causes a more severe fluctuation in electron density, temperature, and collision frequency inside the plasma sheath. However, when the outer scale is close to the thickness of the plasma sheath, the turbulence eddies have almost no influence on the wave propagation. Therefore, the bit error rate (BER) obviously increases with the increase in variance of the refractive index fluctuation and the decrease in the outer scale. These results are fundamental for evaluating the performance of the FSO link under the effect of plasma sheath turbulence.

  8. Instability, Collapse and Oscillation of Sheaths Caused by Secondary Electron Emission

    SciTech Connect

    M.D. Campanell, A.V. Khrabrov and I.D. Kaganovich

    2013-01-03

    The Debye sheath is shown to be unstable under general conditions. For surface materials with sufficient secondary electron emission (SEE) yields, the surface's current-voltage characteristic has an unstable branch when the bulk plasma temperature (Te ) exceeds a critical value, or when there are fast electron populations present. The plasma-surface interaction becomes dynamic where the sheath may undergo spontaneous transitions or oscillations. Using particle-in-cell simulations, we analyze sheath instabilities occurring in a high Te plasma slab bounded by walls with SEE. As the plasma evolves, whenever the sheath enters an unstable state, its amplitude rapidly collapses, allowing a large flux of previously trapped electrons to hit the wall. These hot electrons induce more than one secondary on average, causing a net loss of electrons from the wall. The sheath collapse quenches when the surface charge becomes positive because the attractive field inhibits further electrons from escaping. Sheath instabilities influence the current balance, energy loss, cross-B-field transport and even the bulk plasma properties. Implications for discharges including Hall thrusters are discussed. More generally, the results show that common theories that treat emission as a fixed (time-independent) "coefficient" do not capture the full extent of SEE effects.

  9. A STRUCTURAL ANALYSIS OF THE MYELIN SHEATH IN THE CENTRAL NERVOUS SYSTEM

    PubMed Central

    Hirano, Asao; Dembitzer, Herbert M.

    1967-01-01

    The cerebral white matter of rats subjected to a variety of noxious experimental conditions was examined in the electron microscope. Several unusual configurations of the myelin sheath are identified in addition to the usual configuration. These variations include the presence of (a) formed organelles within the inner and outer loops, (b) isolated islands of cytoplasm in unfused portions of the major dense lines, (c) apparently unconnected cell processes between the sheath and the axon, and (d) concentric, double myelin sheaths. A generalized model of the myelin sheath based on a hypothetical unrolling of the sheath is described. It consists of a shovel-shaped myelin sheet surrounded by a continuous thickened rim of cytoplasm. Most of the unusual myelin configurations are explained as simple variations on this basic theme. With the help of this model, an explanation of the formation of the myelin sheath is offered. This explanation involves the concept that myelin formation can occur at all cytoplasmic areas adjacent to the myelin proper and that adjacent myelin lamellae can move in relation to each other. PMID:6035645

  10. Solid dispersions in the form of electrospun core-sheath nanofibers

    PubMed Central

    Yu, Deng-Guang; Zhu, Li-Min; Branford-White, Christopher J; Yang, Jun-He; Wang, Xia; Li, Ying; Qian, Wei

    2011-01-01

    Background The objective of this investigation was to develop a new type of solid dispersion in the form of core-sheath nanofibers using coaxial electrospinning for poorly water-soluble drugs. Different functional ingredients can be placed in various parts of core-sheath nanofibers to improve synergistically the dissolution and permeation properties of encapsulated drugs and to enable drugs to exert their actions. Methods Using acyclovir as a model drug, polyvinylpyrrolidone as the hydrophilic filament-forming polymer matrix, sodium dodecyl sulfate as a transmembrane enhancer, and sucralose as a sweetener, core-sheath nanofibers were successfully prepared, with the sheath part consisting of polyvinylpyrrolidone, sodium dodecyl sulfate, and sucralose, and the core part composed of polyvinylpyrrolidone and acyclovir. Results The core-sheath nanofibers had an average diameter of 410 ± 94 nm with a uniform structure and smooth surface. Differential scanning calorimetry and x-ray diffraction results demonstrated that acyclovir, sodium dodecyl sulfate, and sucralose were well distributed in the polyvinylpyrrolidone matrix in an amorphous state due to favoring of second-order interactions. In vitro dissolution and permeation studies showed that the core-sheath nanofiber solid dispersions could rapidly release acyclovir within one minute, with an over six-fold increased permeation rate across the sublingual mucosa compared with that of crude acyclovir particles. Conclusion The study reported here provides an example of the systematic design, preparation, characterization, and application of a novel type of solid dispersion consisting of multiple components and structural characteristics. PMID:22228995

  11. [Malignant intracerebral nerve sheath tumours: Two case reports and complete review of the literature cases].

    PubMed

    Le Fèvre, C; Castelli, J; Perrin, C; Hénaux, P L; Noël, G

    2016-04-01

    Malignant peripheral nerve sheath tumours are extremely rare and can be associated with neurofibramatosis type 1. Their prognosis is poor and surgery remains the mainstay of therapy and should be the first line of treatment. Radiotherapy and chemotherapy are second line treatment and their effectiveness remains to demonstrate. The diagnosis is clinical, radiological, histological and immunohistochemical. Malignant peripheral nerve sheath tumours have a potential of local tumour recurrence very high and can metastasize. They often occur in extremity of the members but also rarely into brain. We report two cases of intracerebral nerve sheath tumour. The first was a 68-year-old woman who was admitted with progressive symptoms of headache and diplopia. A left frontotemporal malignant peripheral nerve sheath tumours was diagnosed and was treated by surgery and irradiation. Ten months later, she presented a local recurrence and spine bone's metastases were treated by vertebroplasty and irradiation. The patient died 15 months after the diagnosis. The second case was a 47-year-old woman who was referred because headache and vomiting symptoms. A right frontal malignant peripheral nerve sheath tumours was diagnosed and treated by surgery and irradiation. After that, the patient had three local recurrence operated and pulmonary and cranial bone's metastases. She was still alive after 20 months. We propose a literature review with 25 cases of intracerebral nerve sheath tumour identified, including the two current cases.

  12. GRMHD/RMHD Simulations and Stability of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Hardee, Philip; Mizuno, Yosuke; Nishikawa, Ken-Ichi

    2007-01-01

    A new general relativistic magnetohydrodynamics (GRMHD ) code "RAISHIN" used to simulate jet generation by rotating and non-rotating black holes with a geometrically thin Keplarian accretion disk finds that the jet develops a spine-sheath structure in the rotating black hole case. Spine-sheath structure and strong magnetic fields significantly modify the Kelvin-Helmholtz (KH) velocity shear driven instability. The RAISHIN code has been used in its relativistic magnetohydrodynamic (RMHD) configuration to study the effects of strong magnetic fields and weakly relativistic sheath motion, cl2, on the KH instability associated with a relativistic, Y = 2.5, jet spine-sheath interaction. In the simulations sound speeds up to ? c/3 and Alfven wave speeds up to ? 0.56 c are considered. Numerical simulation results are compared to theoretical predictions from a new normal mode analysis of the RMHD equations. Increased stability of a weakly magnetized system resulting from c/2 sheath speeds and stabilization of a strongly magnetized system resulting from d 2 sheath speeds is found.

  13. A smart core-sheath nanofiber that captures and releases red blood cells from the blood

    NASA Astrophysics Data System (ADS)

    Shi, Q.; Hou, J.; Zhao, C.; Xin, Z.; Jin, J.; Li, C.; Wong, S.-C.; Yin, J.

    2016-01-01

    A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from

  14. Fluid simulation of an electrostatic plasma sheath with two species of positive ions and charged nanoparticles

    SciTech Connect

    Foroutan, G.

    2010-12-15

    One-dimensional fluid simulations are used to study the dynamics of an electrostatic plasma sheath containing nanosized dust grains and two species of positive ions, i.e., He{sup +} and Ar{sup +}. The impacts of the concentration of each species, the velocity at the sheath edge of the ions, and the bias voltage of the substrate, on the spatial distribution of the velocity and number density of the plasma particles, and the incident fluxes of the ions on the substrate, are investigated. The numerical results show that the sheath thickness increases with increasing {sigma}, the density ratio of He{sup +} ions to Ar{sup +} ions at the sheath edge. For nanosized dust particles considered in this work, the dominant forces are the ion drag and the electric force and the effects of the neutral drag and gravity are negligible. Due to enhancement of the ion drag force and the electric force, the dust velocity increases and, consequently, the dust number density decreases as the concentration at the sheath edge of Ar{sup +} ions is increased. For the same velocity and number density at the sheath edge, the number density of Ar{sup +} ions near the wall is larger than that of He{sup +} ions, but their incident fluxes are the same. The maximum in the dust number density increases with the velocity of Ar{sup +} ions at the sheath edge, but it weakly changes with the Mach number of He{sup +} ions, except for large values of {sigma}. The position of the maximum dust number density initially decreases very quickly with increasing the velocity at the sheath edge of the ions from small values, but then at larger values it changes quite slowly. The differences in the sheath parameters for different values of {sigma} disappear at some values of the velocity at the sheath edge of the ions and dust particles. The incident flux of the ions are independent of the bias voltage of the substrate, but their kinetic energy is equal to the bias potential.

  15. Dissolution and immunochemical analysis of the sheath of the archaeobacterium Methanospirillum hungatei GP1.

    PubMed Central

    Southam, G; Beveridge, T J

    1991-01-01

    The sheath of Methanospirillum hungatei GP1 was degraded by three dissolution techniques, which produced a range of soluble products. By using 0.05 M L-arginine buffer (pH 12.6) at 90 degrees C for 10 min, 74% (dry weight) of the sheath was dissolved; however, the solubilized polypeptides were extensively degraded. Treatment with 2% beta-mercaptoethanol and 2% sodium dodecyl sulfate at 90 degrees C in 0.05 M 2(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer (pH 9.0) solubilized 42% (dry weight) of the sheath as a group of polypeptides of 30 to 40 kDa. At 100 degrees C for 2 h, 5% beta-mercaptoethanol, 2% sodium dodecyl sulfate (SDS), and 20 mM EDTA released 74% of the sheath's mass as a group of polypeptides of 10 to 40 kDa. All solubilized products were examined by SDS-polyacrylamide gel electrophoresis, and a range of high- and low-molecular-weight polypeptides was identified. None were glycoproteins. Hoops, which comprise the sheath's structure, were seen by electron microscopy after all of the attempted dissolutions. Monoclonal antibodies were produced against the 10- to 40-kDa range of solubilized products and against the approximately 40-kDa polypeptides, and polyclonal antiserum was produced against an 18-kDa polypeptide. These immunological markers were used in Western immunoblotting and protein A-colloidal gold-antibody probing by electron microscopy to identify the structural location of the various polypeptides. Native sheath, which possesses 2.8-nm particles on its outer surface (M. Stewart, T.J. Beveridge, and G.D. Sprott, J. Mol. Biol. 183:509-515, 1985; P.J. Shaw, G.J. Hills, J.A. Henwood, J.E. Harris, and D.B. Archer, J. Bacteriol. 161:750-757, 1985), presented a gentle wave-form surface in platinum-shadowed specimens. In contrast, the inner face of the sheath was highlighted by ridges lying perpendicular to the longitudinal axis of the sheath and likely corresponded to hoop boundaries. Both the polyclonal and monoclonal antibodies were specific

  16. Fractionated Stereotactic Radiotherapy in Patients With Optic Nerve Sheath Meningioma

    SciTech Connect

    Paulsen, Frank; Doerr, Stefan; Wilhelm, Helmut; Becker, Gerd; Bamberg, Michael; Classen, Johannes

    2012-02-01

    Purpose: To evaluate the effectiveness of fractionated stereotactic radiotherapy (SFRT) in the treatment of optic nerve sheath meningioma (ONSM). Methods and Materials: Between 1993 and 2005, 109 patients (113 eyes) with primary (n = 37) or secondary (n = 76) ONSM were treated according to a prospective protocol with SFRT to a median dose of 54 Gy. All patients underwent radiographic, ophthalmologic, and endocrine analysis before and after SFRT. Radiographic response, visual control, and late side effects were endpoints of the analysis. Results: Median time to last clinical, radiographic, and ophthalmologic follow up was 30.2 months (n = 113), 42.7 months (n = 108), and 53.7 months (n = 91), respectively. Regression of the tumor was observed in 5 eyes and progression in 4 eyes, whereas 104 remained stable. Visual acuity improved in 12, deteriorated in 11, and remained stable in 68 eyes. Mean visual field defects reduced from 33.6% (n = 90) to 17.8% (n = 56) in ipsilateral and from 10% (n = 94) to 6.7% (n = 62) in contralateral eyes. Ocular motility improved in 23, remained stable in 65, and deteriorated in 3 eyes. Radiographic tumor control was 100% at 3 years and 98% at 5 years. Visual acuity was preserved in 94.8% after 3 years and in 90.9% after 5 years. Endocrine function was normal in 90.8% after 3 years and in 81.3% after 5 years. Conclusions: SFRT represents a highly effective treatment for ONSM. Interdisciplinary counseling of the patients is recommended. Because of the high rate of preservation of visual acuity we consider SFRT the standard approach for the treatment of ONSM. Prolonged observation is warranted to more accurately assess late visual impairment. Moderate de-escalation of the radiation dose might improve the preservation of visual acuity and pituitary gland function.

  17. Alterations at chromosome 17 loci in peripheral nerve sheath tumors

    SciTech Connect

    Lothe, R.A.; Slettan, A.; Saeter, G.

    1995-01-01

    Little is known about the molecular genetic changes in malignant peripheral nerve sheath tumors (MPNST). Inactivation of the TP53 gene in l7p has been reported in a few tumors. The MPNST is one of the manifestations of neurofibromatosis 1 (NF1), suggesting that the NF1 gene in 17q might be important. We present a study of 15 neurofibromas and MPNST from nine individuals. Seven patients had NF1 and six of these developed MPNST. Genetic alterations at nine polymorphic loci on chromosome 17 were examined. Allelic imbalance was detected only in the malignant tumors from NF1 patients (4/6). Complete loss of heterozygosity of 17q loci was found in three of these tumors, all including loci within the NF1 gene. Two of the malignant tumors also showed deletions on 17p. No mutations were detected within exon 5-8 of the TP53 in any of the MPNST, and none of them were TP53 protein-positive using immunostaining with mono- and polyclonal antibodies against TP53. The numbers of chromosome 17 present in each tumor were evaluated by use of fluorescence in situ hybridization (FISH) on interphase nuclei with a centromere-specific probe. A deviation from the disomic status of chromosome 17 was observed in two of the MPNST from NF1 patients. These results support the hypothesis of inactivation of both NF1 gene alleles during development of MPNST in patients with NF1. In contrast to other reports, we did not find evidence for a homozygous mutated condition of the TP53 gene in the same tumors. Finally, FISH analysis was in accordance with the DNA analysis in the deduction of the numbers of chromosome 17 in these tumors. 29 refs., 3 figs., 2 tabs.

  18. Metal telescopic and Amplatz sheath dilation in nephrolithotomy.

    PubMed

    Hijazi, Sameh; Echtle, Dieter; Hasselhof, Viktoria M; Trojan, Lutz; Heinrich, Elmar

    2016-01-01

    Comparison of Amplatz sheath percutaneous nephrolithotomy (Amplatz PCNL) and metal telescopic dilation PCNL (MTD PCNL) with respect to clinical outcomes and complications. Single-institution retrospective chart review with 73 patients who underwent PCNL divided into two groups: Amplatz PCNL (n = 26) and MTD PCNL (n = 47). Efficacy (stone-free rate, residual stones, and surgical duration) and safety (transfusion rate and hemoglobin decrease) were evaluated. Complications were recorded and classified using the modified Clavien classification system. The two PCNL groups were similar regarding mean age, stone burden, side, stone location, and stone composition. There were no significant differences in surgery duration (101 ± 28 vs. 98 ± 30 min; P = 0.906), transfusion rate (3.9% vs. 4.3%; P = 0.382), and hemoglobin drop (0.9 ± 0.9 vs. 1 ± 0.7 g/dl; P = 0.424) for Amplatz and MTD PCNL, respectively. Stone-free rate (86% vs. 68%; P = 0.001) was significantly higher while residual fragments rate (37% vs. 60%; P = 0.001) was significantly lower in Amplatz PCNL compared to MTD PCNL. However, tube stay time (4.4 ± 1.8 vs. 5.8 ± 3.6 days; P = 0.005) and hospital time (8.6 ± 2.6 vs. 9.7 ± 5.5 days; P = 0.0001) were significantly longer in Amplatz PCNL compared to MTD PCNL. Clavien grading revealed a significantly higher rate of low-grade complications (I-III) for the MTD PCNL in comparison to Amplatz PCNL (10.6% vs. 3.9%, respectively; P = 0.011). There were no major complications and no tract dilation failure. The study demonstrates that Amplatz PCNL is a safe and effective procedure to remove large renal stones compared with MTD PCNL.

  19. Metal telescopic and Amplatz sheath dilation in nephrolithotomy

    PubMed Central

    Hijazi, Sameh; Echtle, Dieter; Hasselhof, Viktoria M.; Trojan, Lutz; Heinrich, Elmar

    2016-01-01

    Introduction: Comparison of Amplatz sheath percutaneous nephrolithotomy (Amplatz PCNL) and metal telescopic dilation PCNL (MTD PCNL) with respect to clinical outcomes and complications. Materials and Methods: Single-institution retrospective chart review with 73 patients who underwent PCNL divided into two groups: Amplatz PCNL (n = 26) and MTD PCNL (n = 47). Efficacy (stone-free rate, residual stones, and surgical duration) and safety (transfusion rate and hemoglobin decrease) were evaluated. Complications were recorded and classified using the modified Clavien classification system. Results: The two PCNL groups were similar regarding mean age, stone burden, side, stone location, and stone composition. There were no significant differences in surgery duration (101 ± 28 vs. 98 ± 30 min; P = 0.906), transfusion rate (3.9% vs. 4.3%; P = 0.382), and hemoglobin drop (0.9 ± 0.9 vs. 1 ± 0.7 g/dl; P = 0.424) for Amplatz and MTD PCNL, respectively. Stone-free rate (86% vs. 68%; P = 0.001) was significantly higher while residual fragments rate (37% vs. 60%; P = 0.001) was significantly lower in Amplatz PCNL compared to MTD PCNL. However, tube stay time (4.4 ± 1.8 vs. 5.8 ± 3.6 days; P = 0.005) and hospital time (8.6 ± 2.6 vs. 9.7 ± 5.5 days; P = 0.0001) were significantly longer in Amplatz PCNL compared to MTD PCNL. Clavien grading revealed a significantly higher rate of low-grade complications (I–III) for the MTD PCNL in comparison to Amplatz PCNL (10.6% vs. 3.9%, respectively; P = 0.011). There were no major complications and no tract dilation failure. Conclusion: The study demonstrates that Amplatz PCNL is a safe and effective procedure to remove large renal stones compared with MTD PCNL. PMID:26834405

  20. The research and preparation of a bi-layer biodegradable external sheath with directional drug release profiles for vein graft

    NASA Astrophysics Data System (ADS)

    Liu, Zhenjie; Guo, Zhenying; Si, Yi; Zhang, Xiangman; Shi, Zhenyu; Chen, Feng; Fu, Weiguo

    2013-11-01

    External sheath has been suggested for autologous vein grafts to inhibit neointimal hyperplasia and prevent anastomosis stricture. In this study, we prepared a bi-layer biodegradable paclitaxel-loaded sheaths with a synthetic copolymer poly(ethylene carbonate-ɛ-caprolactone) at room temperature. The bi-layer drug release profiles of the Paclitaxel-loaded (PTX-loaded) sheath significantly slow down the paclitaxel (PTX) release rates and result in a directional drug release way. Moreover, the nanofibrous layer of PTX-loaded poly(EC-CL) sheaths reduced the cytotoxicity and provided a better support for fibroblast adhesion and proliferation than the PTX-loaded layer of the sheaths. Thus, this study demonstrates that the bi-layer PTX-loaded poly(EC-CL) sheath with directional drug release profiles have a promising application for vein graft to against neointimal hyperplasia and anastomotic stricture.

  1. Factors affecting the geoeffectiveness of shocks and sheaths at 1 AU

    NASA Astrophysics Data System (ADS)

    Lugaz, N.; Farrugia, C. J.; Winslow, R. M.; Al-Haddad, N.; Kilpua, E. K. J.; Riley, P.

    2016-11-01

    We identify all fast-mode forward shocks, whose sheath regions resulted in a moderate (56 cases) or intense (38 cases) geomagnetic storm during 18.5 years from January 1997 to June 2015. We study their main properties, interplanetary causes, and geoeffects. We find that half (49/94) such shocks are associated with interacting coronal mass ejections (CMEs), as they are either shocks propagating into a preceding CME (35 cases) or a shock propagating into the sheath region of a preceding shock (14 cases). About half (22/45) of the shocks driven by isolated transients and which have geoeffective sheaths compress preexisting southward Bz. Most of the remaining sheaths appear to have planar structures with southward magnetic fields, including some with planar structures consistent with field line draping ahead of the magnetic ejecta. A typical (median) geoeffective shock-sheath structure drives a geomagnetic storm with peak Dst of -88 nT pushes the subsolar magnetopause location to 6.3 RE, i.e., below geosynchronous orbit and is associated with substorms with a peak AL index of -1350 nT. There are some important differences between sheaths associated with CME-CME interaction (stronger storms) and those associated with isolated CMEs (stronger compression of the magnetosphere). We detail six case studies of different types of geoeffective shock-sheaths, as well as two events for which there was no geomagnetic storm but other magnetospheric effects. Finally, we discuss our results in terms of space weather forecasting and potential effects on Earth's radiation belts.

  2. Evaluation of practice efficiency with a novel sheathed flexible cystoscope: a randomized controlled trial.

    PubMed

    Krebs, Alfred; Borin, James F; Kim, Isaac Y; Jackson, Donna J; McDougall, Elspeth M; Clayman, Ralph V

    2007-11-01

    The processing of standard flexible cystoscopes is time-consuming and potentially hazardous to healthcare staff. We evaluated a novel flexible cystoscope system containing a disposable sheath, which obviates the need for chemical processing. A total of 100 patients undergoing office cystoscopy were randomized into a "sheath" or a control group (n = 50 for each group). Disposable Slide-On sheaths and the CST-2000 Flexible Cystoscope System were used in the former group. A standard 16F flexible cystoscope, manually cleaned and disinfected with Cidex OPA or Rapicide, was used in the control group and the preparation times were recorded. Questionnaires to assess cystoscope setup, handling, optical quality, and patient comfort were completed by the physician, nursing staff, and patients. Data were available for 97 patients. The mean total time required for preparation of the cystoscopes was 10.7, 14.7, and 42.2 minutes for the sheath (n = 49), Rapicide (n = 21), and Cidex OPA (n = 27), respectively (P <0.01 for all comparisons). The control group scored better than the sheath group with regard to ease of cystoscope insertion (9.1 versus 7.7), cystoscope handling (8.8 versus 8.1), and irrigation setup (8.8 versus 8.2; all P < or = 0.01). No statistically significant difference was found between groups for procedure time, optical quality, or patient comfort, either during or after the procedure. The EndoSheath System can save 4 to 31 minutes of processing time while avoiding exposure to irritants found in conventional soaking methods. Although maneuvering of the sheathed cystoscope was slightly more difficult, the optical quality and patient comfort were similar to those of standard flexible cystoscopy.

  3. Variable stiffness outer sheath with "Dragon skin" structure and negative pneumatic shape-locking mechanism.

    PubMed

    Zuo, Siyang; Iijima, Kazuo; Tokumiya, Takahiro; Masamune, Ken

    2014-09-01

       Natural orifice transluminal endoscopic surgery (NOTES) offers the possibility of surgery without visible scars. To overcome the limitations of NOTES, we developed a novel surgical device called the rigid and flexible outer sheath with multi-piercing surgery (MPS).    This sheath can switch between flexible and rigid modes using a novel "Dragon skin" structure and a negative pneumatic shape-locking mechanism. In addition, it has an integrated bending structure that enables it to flex in four directions at the distal end. The insertion part of the prototype is 575 mm long with a 20 mm outer diameter. The rigid and flexible shaft is separated into two parts. The primary and secondary shape-locking shafts are 300 and 200 mm long, respectively. The two parts of shape-locking shaft can be locked independently, including both being locked simultaneously. In addition, the model was equipped with one 7- and 1.7-mm-diameter, and three 3-mm-diameter working channels. When the sheath approaches the target, the surgeon locks the shape and then easily inserts flexible instruments through the path created by the sheath. In this study, we evaluated the stiffness of the prototype. Furthermore, an in vivo partial gastrectomy experiment was also performed.    The experimental results regarding the shape property suggest that the rigidity of the shaft was considerably increased using this mechanism. An in vivo partial gastrectomy experiment performed using a swine was successfully performed using the outer sheath for assistance. The outer sheath was inserted through a percutaneous route during the in vivo experiment.    The evaluation results show that the advanced outer sheath system has great promise for solving access and stability problems with NOTES.

  4. Ultrasound-guided rectus sheath block in children with umbilical hernia: Case series.

    PubMed

    Alsaeed, Abdul Hamid; Thallaj, Ahmed; Khalil, Nancy; Almutaq, Nada; Aljazaeri, Ayman

    2013-10-01

    Umbilical hernia repair, a common day-case surgery procedure in children, is associated with a significant postoperative pain. The most popular peripheral nerve blocks used in umbilical hernia repair are rectus sheath infiltration and caudal block. The rectus sheath block may offer improved pain relief following umbilical hernia repair with no undesired effects such as lower limb motor weakness or urinary retention seen with caudal block which might delay discharge from the hospital. Ultrasound guidance of peripheral nerve blocks has reduced the number of complications and improved the quality of blocks. The aim of this case series is to assess the post rectus sheath block pain relief in pediatric patients coming for umbilical surgery. Twenty two (22) children (age range: 1.5-8 years) scheduled for umbilical hernia repair were included in the study. Following the induction of general anesthesia, the ultrasonographic anatomy of the umbilical region was studied with a 5-16 MHz 50 mm linear probe. An ultrasound-guided posterior rectus sheath block of both rectus abdominis muscles (RMs) was performed (total of 44 punctures). An in-plain technique using Stimuplex A insulated facet tip needle 22G 50mm. Surgical conditions, intraoperative hemodynamic parameters, and postoperative analgesia by means of the modified CHEOPS scale were evaluated. ultrasonograghic visualization of the posterior sheath was possible in all patients. The ultrasound guided rectus sheath blockade provided sufficient analgesia in all children with no need for additional analgesia except for one patient who postoperatively required morphine 0.1 mg/kg intravenously. There were no complications. Ultrasound guidance enables performances of an effective rectus sheath block for umbilical hernia. Use of the Stimuplex A insulated facet tip needle 22G 50mm provides easy, less traumatic skin and rectus muscle penetration and satisfactory needle visualiza.

  5. A direct nitinol stent delivery technique for endovascular treatment: a sheath-less stenting technique.

    PubMed

    Shintani, Yoshiaki; Kawasaki, Tomohiro; Fujimura, Takashi; Ishida, Kouichirou; Higuchi, Takanori; Kajiwara, Masataka; Fukuoka, Ryota; Orita, Yoshiya; Umeji, Kyoko; Koga, Hisashi; Koga, Nobuhiko

    2015-04-01

    Access site problems often cause serious complications in endovascular treatment. The aim of this study is to investigate whether a sheath-less nitinol stenting technique leads to reduce access site complications. This study was a single-center retrospective analysis of a prospectively maintained database. The study enrolled consecutive 98 patients with 111 lesions undergoing provisional stenting for de novo iliac artery or femoro-popliteal artery stenosis between August 2010 and November 2011. The patients were divided into two groups, a conventional procedure group and a sheath-less procedure group. The outcomes of this study were peri-procedural access site complications, initial success rate, procedure time, hemostatic time and bed-rest time. Forty-four lesions in 39 patients that treated using the sheath-less nitinol stent delivery technique were compared with 67 lesions in 59 patients treated using the conventional procedure. All procedures were successful. The incidence of pseudoaneurysm was significantly lower in the sheath-less procedure group than in the conventional procedure group (p = 0.043). However, there were no significant differences in any other complications. No significant difference was observed in the procedural time (p = 0.309). However, hemostatic time and bed-rest time were significantly shorter in the sheath-less procedure than in the conventional procedure (p < 0.0001). A sheath-less stenting technique reduced the access site incidence of pseudoaneurysm and did not increase other access site complications. Besides, this technique shortened hemostatic time and bed-rest time. The sheath-less stenting technique is considered to be a useful method for endovascular treatment.

  6. Head lice: scientific assessment of the nit sheath with clinical ramifications and therapeutic options.

    PubMed

    Burkhart, Craig N; Burkhart, Craig G

    2005-07-01

    Head lice, like many insects, produce a protective coating for their newly laid eggs that is essential to the survival of the species. Knowledge of the composition of the sheath, which is the glue by which the egg is attached to human hair, and the nit laying process could lead to production of agents that could be used to attack louse infestations by interfering with the normally protected environment of nymph development within the egg. The physical removal of nits has become an important part of treatment of head louse infestations given the "no-nit" policy in schools. Biochemical analysis has revealed that the nit sheath of the head louse is composed of 4 bands of protein, possibly cross-linked to aliphatic components with a tertiary structure of beta sheeting. Nature has protected the louse by making the nit sheath similar in composition to the hair; thereby, agents designed to unravel the nit sheath may also damage human hair. Possible targets to destroy the nit sheath include proteases, denaturants, beta sheet breaker proteins, and small protein inhibitors of sheath formation. Better understanding of insect glues may allow us to develop compounds so that the liquid secretions of the collateral glands of the female louse, which becomes the nit sheath, do not solidify by oxidation when placed with the louse egg onto human hair. Knowledge of insect behavior, such as oviposition, may also suggest methods for repelling female lice from laying eggs onto hair. Alternatively, agents that coat the nits and restrict the oxygen transfer to the developing larvae may prove beneficial.

  7. Variation of mechanical properties of the metallic sheath in composite Ag/BSCCO tapes during plastic conformation

    NASA Astrophysics Data System (ADS)

    Hassan, Mohamed K.; Navarro, Rafael

    2002-08-01

    The evolution of the mechanical properties of Ag/BSCCO monocore composites, during powder in tube conformation by wire drawing and free ends tape rolling is analysed. Results on composite wires and tapes with different thickness of the cladding sheaths and on a reference empty tube are reported. The properties of the metallic sheaths and of the compact powder cores are characterised. A correlation of the variations induced in the sheaths by the overall plastic work per unit volume is outlined.

  8. Evolution of Piled-up Compressions in Modeled Coronal Mass Ejection Sheaths and the Resulting Sheath Structures

    NASA Astrophysics Data System (ADS)

    Das, Indrajit; Opher, Merav; Evans, Rebekah; Loesch, Cristiane; Gombosi, Tamas I.

    2011-03-01

    We study coronal mass ejection (CME)-driven shocks and the resulting post-shock structures in the lower corona (2-7 R sun). Two CMEs are erupted by modified Titov-Démoulin (TD) and Gibson-Low (GL) type flux ropes (FRs) with the Space Weather Modeling Framework. We observe a substantial pile-up of density compression and a narrow region of plasma depletion layer (PDL) in the simulations. As the CME/FR moves and expands in the solar wind medium, it pushes the magnetized material lying ahead of it. Hence, the magnetic field lines draping around the CME front are compressed in the sheath just ahead of the CME. These compressed field lines squeeze out the plasma sideways, forming PDL in the region. Solar plasma being pushed and displaced from behind forms a strong piled-up compression (PUC) of density downstream of the PDL. Both CMEs have comparable propagation speeds, while GL has larger expansion speed than TD due to its higher initial magnetic pressure. We argue that high CME expansion speed along with high solar wind density in the region is responsible for the large PUC found in the lower corona. In case of GL, the PUC is much wider, although the density compression ratio for both the cases is comparable. Although these simulations artificially initiate out-of-equilibrium CMEs and drive them in an artificial solar wind solution, we predict that PUCs, in general, will be large in the lower corona. This should affect the ion profiles of the accelerated solar energetic particles.

  9. Penetration of Günther Tulip filter struts through an introducer sheath: case report and safety concerns.

    PubMed

    Contractor, Sohail G; Merkulov, Alex; Bhatti, Waseem; Lee, Michael; Gardner, Kim

    2009-08-01

    The authors present a patient who had a Günther-Tulip inferior vena cava filter placed under fluoroscopic guidance. The filter struts were seen to penetrate through the introducer sheath at deployment. This was believed to be secondary to a kink in the sheath at the site of venous entry and was due to the patient's nuchal obesity as well as his inability to turn his head to the opposite side. The introducer sheath was then placed through a long reinforced metal sheath through which the filter was then placed without complication.

  10. Relationship between myelin sheath diameter and internodal length in axons of the anterior medullary velum of the adult rat.

    PubMed

    Ibrahim, M; Butt, A M; Berry, M

    1995-11-01

    Relations between myelin sheath diameters and internodal lengths were measured in whole mounts of osmium stained intact anterior medullary velum (AMV) from glutaraldehyde perfused adult rats. The AMV is a sheet of CNS tissue which roofs the IVth ventricle and contains fascicles of myelinated fibres which arise mainly from the nucleus of the IVth cranial nerve. These fibers displayed a broad range of myelin sheath external diameters and internodal lengths, from < 1-12 microns and 50-750 microns, respectively. Myelin sheath external diameter was a measurement of the axonal diameter plus the thickness of its myelin sheath, while internodal length was measured as the distance between consecutive nodes. There was a broadly linear relationship between myelin sheath diameters and internodal lengths, with the smaller diameter sheaths tending to have shorter internodes than the larger. However, the correlation was weak and for any given diameter myelin sheaths displayed considerable variation in their internodal lengths. The smallest diameter myelin sheaths, < 4 microns, consistently had shorter internodes than predicted by a linear regression and, in an analysis of consecutive internodes in single fibres, the slope was flattened in fibres with a diameter > 4 microns. Our results indicated that small and large calibre fibres may have different myelin sheath diameter-internodal length interrelations.

  11. Quantitative modeling of ICRF antennas with integrated time domain RF sheath and plasma physics

    NASA Astrophysics Data System (ADS)

    Smithe, David N.; D'Ippolito, Daniel A.; Myra, James R.

    2014-02-01

    Significant efforts have been made to quantitatively benchmark the sheath sub-grid model used in our time-domain simulations of plasma-immersed antenna near fields, which includes highly detailed three-dimensional geometry, the presence of the slow wave, and the non-linear evolution of the sheath potential. We present both our quantitative benchmarking strategy, and results for the ITER antenna configuration, including detailed maps of electric field, and sheath potential along the entire antenna structure. Our method is based upon a time-domain linear plasma model [1], using the finite-difference electromagnetic Vorpal/Vsim software [2]. This model has been augmented with a non-linear rf-sheath sub-grid model [3], which provides a self-consistent boundary condition for plasma current where it exists in proximity to metallic surfaces. Very early, this algorithm was designed and demonstrated to work on very complicated three-dimensional geometry, derived from CAD or other complex description of actual hardware, including ITER antennas. Initial work with the simulation model has also provided a confirmation of the existence of propagating slow waves [4] in the low density edge region, which can significantly impact the strength of the rf-sheath potential, which is thought to contribute to impurity generation. Our sheath algorithm is based upon per-point lumped-circuit parameters for which we have estimates and general understanding, but which allow for some tuning and fitting. We are now engaged in a careful benchmarking of the algorithm against known analytic models and existing computational techniques [5] to insure that the predictions of rf-sheath voltage are quantitatively consistent and believable, especially where slow waves share in the field with the fast wave. Currently in progress, an addition to the plasma force response accounting for the sheath potential, should enable the modeling of sheath plasma waves, a predicted additional root to the dispersion

  12. Quantitative modeling of ICRF antennas with integrated time domain RF sheath and plasma physics

    SciTech Connect

    Smithe, David N.; D'Ippolito, Daniel A.; Myra, James R.

    2014-02-12

    Significant efforts have been made to quantitatively benchmark the sheath sub-grid model used in our time-domain simulations of plasma-immersed antenna near fields, which includes highly detailed three-dimensional geometry, the presence of the slow wave, and the non-linear evolution of the sheath potential. We present both our quantitative benchmarking strategy, and results for the ITER antenna configuration, including detailed maps of electric field, and sheath potential along the entire antenna structure. Our method is based upon a time-domain linear plasma model, using the finite-difference electromagnetic Vorpal/Vsim software. This model has been augmented with a non-linear rf-sheath sub-grid model, which provides a self-consistent boundary condition for plasma current where it exists in proximity to metallic surfaces. Very early, this algorithm was designed and demonstrated to work on very complicated three-dimensional geometry, derived from CAD or other complex description of actual hardware, including ITER antennas. Initial work with the simulation model has also provided a confirmation of the existence of propagating slow waves in the low density edge region, which can significantly impact the strength of the rf-sheath potential, which is thought to contribute to impurity generation. Our sheath algorithm is based upon per-point lumped-circuit parameters for which we have estimates and general understanding, but which allow for some tuning and fitting. We are now engaged in a careful benchmarking of the algorithm against known analytic models and existing computational techniques to insure that the predictions of rf-sheath voltage are quantitatively consistent and believable, especially where slow waves share in the field with the fast wave. Currently in progress, an addition to the plasma force response accounting for the sheath potential, should enable the modeling of sheath plasma waves, a predicted additional root to the dispersion, existing at the

  13. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    NASA Astrophysics Data System (ADS)

    Křivská, A.; Bobkov, V.; Colas, L.; Jacquot, J.; Milanesio, D.; Ochoukov, R.

    2015-12-01

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  14. Photosynthetic Gas Exchange Characteristics of Wheat Flag Leaf Blades and Sheaths during Grain Filling

    PubMed Central

    Araus, José L.; Tapia, Luis

    1987-01-01

    The rate of net CO2 assimilation (A), the stomatal (gs) and residual (gr) conductances to CO2, the intercellular CO2 concentration, the CO2 compensation points at 21% O2 (Γ21) and at 2% O2 (Γ2), and the amounts of dry matter, nitrogen, and carbohydrates were determined, from anthesis through grain filling, in the flag leaf blade and sheath of spring wheat (Triticum aestivum L. cv Kolibri). The nitrogen content and the rate of net CO2 assimilation declined slowly until the onset of senescence in both organs, about 3 weeks after anthesis. During senescence the reduction of A in both organs was not primarily caused by a decrease in gs; the main factor is the decrease in gr. From values of Γ21 and Γ2 it is suggested that the rate of respiration in the light contributing to the CO2 compensation point is higher in sheaths than in blades irrespective of the O2 level considered. The role of sheaths storing and later transporting assimilates to the developing grains seems to be more important for shoot yield than that of sheaths functioning as photosynthetic organs after the onset of senescence occurs. It is suggested that accumulation of carbohydrates in leaves might somehow trigger senescence in the flag leaf blade and sheath simultaneously. PMID:16665757

  15. Fully kinetic model of breakdown during sheath expansion after interruption of vacuum arcs

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxing; Wang, Haoran; Zhou, Zhipeng; Tian, Yunbo; Geng, Yingsan; Wang, Jianhua; Liu, Zhiyuan

    2016-08-01

    Research on sheath expansion is critical to the understanding of the dielectric recovery process in a vacuum interrupter after interruption of vacuum arcs. In this paper, we investigated how residual plasma affects breakdown in the sheath expansion period after the current zero. To simulate sheath expansion and breakdown, we developed a fully kinetic particle-in-cell Monte Carlo collision model with one spatial dimension and three velocity dimensions. The model accounted for various collisions, including ionization, excitation, elastic collisions, charge exchange, and momentum exchange, and we added an external circuit to the model to make the calculations self-consistent. The existence of metal vapor slowed the sheath expansion in the gap and caused high electric field formation in front of the cathode surface. The initial residual plasma, which was at sufficiently low density, seemed to have a limited impact on breakdown, and the metal vapor dominated the breakdown in this case. Additionally, the breakdown probability was sensitive to the initial plasma density if the value exceeded a specific threshold, and plasma at sufficiently high density could mean that breakdown would occur more easily. We found that if the simulation does not take the residual plasma into account, it could overestimate the critical value of the metal vapor density, which is always used to describe the boundary of breakdown after interruption of vacuum arcs. We discussed the breakdown mechanism in sheath expansion, and the breakdown is determined by a combination of metal vapor, residual plasma, and the electric field in front of the cathode surface.

  16. Elongation growth of the leaf sheath base of Avena sativa seedlings: regulation by hormones and sucrose

    NASA Technical Reports Server (NTRS)

    Brock, T. G.; Kaufman, P. B.

    1991-01-01

    The leaf sheath base of the seedling of Avena sativa was characterized for growth response to hormones and sucrose. Six day old plants, raised under a 10:14 hr light:dark cycle, were excised at the coleoptilar node and 1 cm above the node for treatment. The growth of the leaf sheath base was promoted by gibberellic acid (GA3) and this response was dose dependent. The lag to response initiation was approximately 4 hr. Growth with or without GA3 (10 micromoles) was transient, diminishing appreciably after 48 hr. The addition of 10 mM sucrose greatly prolonged growth; the effect of GA3 and sucrose was additive. Neither indole-3-acetic acid (IAA) nor the cytokinin N6-benzyladenine (BA), alone or in combination, promoted the growth of leaf sheath bases. However, both significantly inhibited the action of GA3. The inhibitory effect of IAA was dose dependent and was not affected by the addition of BA or sucrose. These results indicate that the growth of leaf sheath bases of Avena sativa is promoted specifically by gibberellin, that this action depends on the availability of carbohydrates from outside of the leaf sheath base, and that the promotional effect of GA3 can be modified by either auxins or cytokinins.

  17. Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

  18. Numerical study of an electrostatic plasma sheath containing two species of charged dust particles

    SciTech Connect

    Foroutan, G.; Akhoundi, A.

    2012-10-01

    A multi-fluid model is used to study the dynamics of a dusty plasma sheath consists of electrons, ions, and two species of charged dust particles, i.e., nano-size and micron-size particles. It is found that, when the sheath is dominated by the nano-size dust grains, spatially periodic fluctuations are developed in the profiles of the sheath potential, and the number density and velocity of the plasma and dust particles. Due to inertial effects, the fluctuations in the parameters of the micron-size grains are much lower than those of the other parameters. The competition between the electric and ion drag forces plays the primary role in development of the fluctuations. The spatial period of the fluctuations is approximately a few Debye lengths and their amplitude depends on the plasma and dust parameters. The fluctuations are reduced by the increase in the radius, mass density, and Mach number of the nano-size particles, as well as the density and Mach number of the ions. But, they are enhanced by the increase in the plasma number density and the electron temperature. The sheath thickness demonstrates a non-monotonic behavior against variation of the nanoparticle parameters, i.e., it first decreases quickly, shows a minimum, and then increases. However, the sheath width always decreases with the plasma number density and ion Mach number, while grows linearly with the electron temperature.

  19. Dissolution Rate of Steel Sheathing Through Plunging and Melt-Through Methods

    NASA Astrophysics Data System (ADS)

    Rivera-Martínez, Elis A.; Beers, Mark; Scheller, Eric; Yu, Edward

    2017-08-01

    In an effort to determine the dissolution rate of the steel sheathing used in the production of cored wire, several experiments were conducted in the ASK Chemicals Metals Application Lab (MAL), in Dublin, Ohio. It is essential to understand that, when exposed to molten metal at a certain temperature/time, the low-carbon steel will dissolve, thereby exposing the contained alloy to the molten metal. This article presents two separate experiments that will provide a better understanding of the dissolution rates of the steel sheathing used in the 9-mm cored wire. The first experiment was an immersion test, where the finished product (cored wire containing a ferroalloy) was submerged in molten metal for a predetermined amount of time. The length of the cored wire was measured before and after the immersion to gauge the effect of time and temperature on the dissolution characteristics. The second experiment was conducted to examine the time and temperature needed to melt through a flat piece of metal sheathing. For this experiment, a flat piece of metal sheathing was placed over the down sprue of a sand-based pouring box. The basin was filled with molten metal at a predetermined temperature, and a high-speed camera and high-temperature thermocouples were used to record the temperature and the time needed to dissolve the metal sheathing.

  20. Analysis of Particle Detectors in Plasma Sheaths on Sounding Rockets and in Laboratory Plasmas

    NASA Astrophysics Data System (ADS)

    Fisher, Lisa; Lynch, Kristina

    2013-10-01

    The influence of plasma sheaths on particle measurements is a well-known problem. Improvements in computational speed and memory have made the use of particle-in-cell codes, attainable on a laptop. These codes can calculate complex sheath structures and include most of the relevant physics. We will discuss how the use of one such code, SPIS, has been integrated into our data processing for the MICA sounding rocket. This inclusion of sheath physics has allowed us to describe the current-voltage signature of an ion retarding potential analyzer, called the PIP, to measure the ambient ionospheric temperature, as well as to examine the possibility of ion upflow. These results will be compared with the other instrumentation on MICA, which use traditional thin-sheath approximations. This comparison will emphasize the strengths and weaknesses of these other data analysis methods and call attention to the need to include sheath physics when measuring very low energy populations. Additionally, these instruments have also been tested in the Dartmouth College plasma facility. This provides another set of plasma conditions for testing and extrapolating our method to a future low-orbit mission.

  1. Successful removal of an entrapped rotablation burr by extracting drive shaft sheath followed by balloon dilatation.

    PubMed

    Sakakura, Kenichi; Ako, Junya; Momomura, Shin-ichi

    2011-10-01

    Burr entrapment is a rare but serious complication during rotational atherectomy (RA). Although emergent surgical removal is a reliable option for this complication, surgical removal is invasive and takes several hours. Balloon inflation just proximal to the burr was the previously-reported nonsurgical option for burr removal. However, this method needed large guide catheter lumen (≥8 Fr). We present a case of 67-year-old male on chronic hemodialysis. During RA for severe stenosis of the right coronary artery, the RA burr was entrapped. We cut off the drive shaft, the drive shaft sheath, and the RA wire together near the advancer, and then we removed the drive shaft sheath. After removing the drive shaft sheath, the 2.5 mm balloon easily entered the 7-Fr guide catheter. We inflated that balloon to a pressure of 18 atm. The burr was easily removed immediately after balloon deflation. Removal of the drive shaft sheath following balloon dilatation is a new, nonsurgical bailout method for a burr that becomes entrapped during RA. Since removal of the drive shaft sheath following balloon dilatation can be applied to 7 Fr as well as 6 Fr guide systems, this method may be of considerable benefit when operators use 7 Fr or 6 Fr systems.

  2. Complications with flush-mounted probe analysis beyond sheath-expansion

    NASA Astrophysics Data System (ADS)

    Kuang, A. Q.; Labombard, B.; Brunner, D.

    2016-10-01

    In a reactor relevant divertor, the heat-flux onto the target plate would be too large and traditional proud Langmuir probes will melt. By making the probes flush with the surface of the target plate they become nearly as robust as the divertor plates themselves. However, without a theoretically rigorous derivation of the sheath thickness, sheath expansion has been a primary concern for the interpretation of flush mounted probe data. Following the installation of a flush-mounted Langmuir probe system at Alcator C-Mod (toroidally-elongated and field-aligned to give it a `rail' geometry) that effectively mitigates the effects of sheath expansion down to incident field line angles of 0.5 degree, further complications have arisen that cannot be explained by sheath-expansion. The `rail' probes systematically measure lower densities and higher temperatures but have the same pressure. The evolution of the scrape-off layer profiles measured on the divertor target plate from sheath-limited to detached regimes is also different. These are indicative of important physics, perhaps unique to conditions in a vertical-target plate divertor with small field-line attack angles, that affects the I-V characteristics and is not currently included in probe data analyses. Controlled experiments performed at Alcator C-Mod mapped out this discrepancy and the results will be presented. Supported by USDoE Awards DE-FC02-99ER54512.

  3. Rectus sheath hematoma with low molecular weight heparin administration: a case series.

    PubMed

    Sullivan, Laura E J; Wortham, Dale C; Litton, Kayleigh M

    2014-09-01

    Rectus sheath hematoma is an uncommon but potentially serious bleeding complication that can occur spontaneously or as a result of anticoagulation administration. Case number one: A 62 year old chronically ill Caucasian female develops a rectus sheath hematoma seven days after hospital discharge. The previous hospitalization included low molecular weight heparin administration for deep vein thrombosis prophylaxis. The patient ultimately chooses comfort care and expires due to sepsis and respiratory failure. Case number two: A 79 year old Caucasian male develops a rectus sheath hematoma during hospital admission where LMWH is used for deep vein thrombosis prophylaxis. He is managed conservatively; however, his hematocrit drops from 46 to 25.8%. Case number three: A 44 year old chronically ill Caucasian female is treated with therapeutic low molecular weight heparin for recent deep vein thrombosis during a hospital admission. She develops a large rectus sheath hematoma requiring embolization as well as blood transfusion. We believe this reflects an underreported significant cause of morbidity and mortality with low molecular weight heparin administration. We review the pathophysiology of rectus sheath hematoma as well as its presentation, diagnosis, and treatment. We identify at-risk populations and proposed contributing factors. We also discuss factors leading to underreporting as well as preventive strategies implemented at our institution.

  4. Changes in myelin sheath thickness and internode geometry in the rabbit phrenic nerve during growth.

    PubMed Central

    Friede, R L; Brzoska, J; Hartmann, U

    1985-01-01

    The rabbit phrenic nerve was studied at seven phases of growth from the newborn to the adult to determine the length of the nerve fibres, the length of the internodes, the fibre calibre, the geometric proportions of the internodes and the thickness of the myelin sheaths. The elongation of the internodes corresponded precisely to the elongation of the nerve, indicating a constant number of approximately 140 internodes per fibre, each internode elongating commensurate with body growth. Internode elongation was accompanied by increases in fibre calibre, but these parameters did not change in precise proportion. The internodes of thick fibres were relatively short for calibre, as defined by the length/diameter quotient. This trend of foreshortening changed during growth. Sheath thickness, defined by the quotient axon diameter/fibre diameter, was determined with a computer-assisted method. Fibres of young rabbits had relatively thin sheaths for axon calibre, compared with adult rabbits. The changes in sheath thickness corresponded to the changes in internode geometry. This was consistent with previous studies showing that elongation or foreshortening of an internode of a given calibre has a slight, but definite effect on the thickness of its myelin sheath. PMID:3870716

  5. Effect of the q-nonextensive electron velocity distribution on a magnetized plasma sheath

    SciTech Connect

    Safa, N. Navab Ghomi, H.; Niknam, A. R.

    2014-08-15

    In this work, a sheath model has been developed to investigate the effect of the q-nonextensive electron velocity distribution on the different characteristics of a magnetized plasma. By using Segdeev potential method, a modified Bohm criterion for a magnetized plasma with the nonextensive electron velocity distribution is derived. The sheath model is then used to analyze numerically the sheath structure under different q, the parameter quantifying the nonextensivity degree of the system. The results show that as the q-parameter decreases, the floating potential becomes more negative. The sheath length increases at the lower values of the q-parameter due to the increase in the electron population at the high-energy tail of the distribution function. As q-parameter decreases, the effective temperature of the electrons increases which results in a more extended plasma sheath. The ion velocity and density profiles for the different nonextensivity degrees of the system reflect the gyro-motion of the ions in the presence of the magnetic field. Furthermore, the results coincide with those given by the Maxwellian electron distribution function, when q tends to 1.

  6. Effect of sheath gas in atmospheric-pressure plasma jet for potato sprouting suppression

    NASA Astrophysics Data System (ADS)

    Nishiyama, S.; Monma, M.; Sasaki, K.

    2016-09-01

    Recently, low-temperature atmospheric-pressure plasma jets (APPJs) attract much interest for medical and agricultural applications. We try to apply APPJs for the suppression of potato sprouting in the long-term storage. In this study, we investigated the effect of sheath gas in APPJ on the suppression efficiency of the potato sprouting. Our APPJ was composed of an insulated thin wire electrode, a glass tube, a grounded electrode which was wound on the glass tube, and a sheath gas nozzle which was attached at the end of the glass tube. The wire electrode was connected to a rectangular-waveform power supply at a frequency of 3 kHz and a voltage of +/- 7 kV. Helium was fed through the glass tube, while we tested dry nitrogen, humid nitrogen, and oxygen as the sheath gas. Eyes of potatoes were irradiated by APPJ for 60 seconds. The sprouting probability was evaluated at two weeks after the plasma irradiation. The sprouting probability was 28% when we employed no sheath gases, whereas an improved probability of 10% was obtained when we applied dry nitrogen as the sheath gas. Optical emission spectroscopy was carried out to diagnose the plasma jet. It was suggested that reactive species originated from nitrogen worked for the efficient suppression of the potato sprouting.

  7. Anode sheath transition in an anodic arc for synthesis of nanomaterials

    NASA Astrophysics Data System (ADS)

    Nemchinsky, V. A.; Raitses, Y.

    2016-06-01

    The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium.

  8. Dissolution Rate of Steel Sheathing Through Plunging and Melt-Through Methods

    NASA Astrophysics Data System (ADS)

    Rivera-Martínez, Elis A.; Beers, Mark; Scheller, Eric; Yu, Edward

    2017-10-01

    In an effort to determine the dissolution rate of the steel sheathing used in the production of cored wire, several experiments were conducted in the ASK Chemicals Metals Application Lab (MAL), in Dublin, Ohio. It is essential to understand that, when exposed to molten metal at a certain temperature/time, the low-carbon steel will dissolve, thereby exposing the contained alloy to the molten metal. This article presents two separate experiments that will provide a better understanding of the dissolution rates of the steel sheathing used in the 9-mm cored wire. The first experiment was an immersion test, where the finished product (cored wire containing a ferroalloy) was submerged in molten metal for a predetermined amount of time. The length of the cored wire was measured before and after the immersion to gauge the effect of time and temperature on the dissolution characteristics. The second experiment was conducted to examine the time and temperature needed to melt through a flat piece of metal sheathing. For this experiment, a flat piece of metal sheathing was placed over the down sprue of a sand-based pouring box. The basin was filled with molten metal at a predetermined temperature, and a high-speed camera and high-temperature thermocouples were used to record the temperature and the time needed to dissolve the metal sheathing.

  9. Speculations on a possible essential function of the gelatinous sheath of blue-green algae.

    PubMed

    Lange, W

    1976-08-01

    Voluminous and often fluffy sheaths surrounding blue-green algal cells are observed (a) in productive natural waters, (b) in bacteria-containing laboratory cultures growing in inorganic nutrient media with added bacteria-assimilable organic matter, and (c) in axenic cultures in the same inorganic media even without added organic matter. The sheaths of bacteria-associated species in inorganic media without added organic matter are, by comparison, thin, and growth is meager. Repeated observations show that voluminous sheaths and vigorous growth of algal species are associated. It is suggested that formation and retention of a voluminous shealth provide a microenvironment around the algal cell where essential nutrients, present at only submarginal levels in the surrounding water, are concentrated and become readily available to the cell. The increase in nutrient concentration above a critical level, in turn, leads to vigorous algal growth. The voluminous sheath produced by the alga is not attacked by alga-associated bacteria when other assimilable organic matter is available; but in the absence of a more suitalble food, the bacteria feed on the less desirable gelatinous sheath, markedly reducing its thickness and causing meager algal growth.

  10. The structural sheath protein of aphids is required for phloem feeding.

    PubMed

    Will, Torsten; Vilcinskas, Andreas

    2015-02-01

    Aphids produce two types of saliva that mediate their interactions with plants. Watery saliva is secreted during cell penetration and ingestion, whereas gel saliva is secreted during stylet movement through the apoplast where it forms a sheath around the stylet to facilitate penetration and seal puncture sites on cell membranes. In order to study the function of the sheath when aphids interact with plants, we used RNA interference (RNAi) to silence the aphid structural sheath protein (SHP) in the pea aphid Acyrthosiphon pisum. The injection of 50 ng of double stranded RNA completely disrupted sheath formation, as confirmed by scanning electron microscopy. Aphid behavior was monitored using the electrical penetration graph technique, revealing that disrupted sheath formation prevented efficient long-term feeding from sieve tubes, with a silencing effect on reproduction but not survival. We propose that sealing the stylet penetration site in the sieve tube plasma membrane is part of a two-step mechanism to suppress sieve-tube occlusion by preventing calcium influx into the sieve tube lumen. The SHP is present in several aphid species and silencing has a similar impact to aphid-resistant plants, suggesting that SHP is an excellent target for RNAi-mediated pest control.

  11. A Coupled MHD and Thermal Model Including Electrostatic Sheath for Magnetoplasmadynamic Thruster Simulation

    NASA Astrophysics Data System (ADS)

    Kawasaki, Akira; Kubota, Kenichi; Funaki, Ikkoh; Okuno, Yoshihiro

    2016-09-01

    Steady-state and self-field magnetoplasmadynamic (MPD) thruster, which utilizes high-intensity direct-current (DC) discharge, is one of the prospective candidates of future high-power electric propulsion devices. In order to accurately assess the thrust performance and the electrode temperature, input electric power and wall heat flux must correctly be evaluated where electrostatic sheaths formed in close proximity of the electrodes affect these quantities. Conventional model simulates only plasma flows occurring in MPD thrusters with the absence of electrostatic sheath consideration. Therefore, this study extends the conventional model to a coupled magnetohydrodynamic (MHD) and thermal model by incorporating the phenomena relevant to the electrostatic sheaths. The sheaths are implemented as boundary condition of the MHD model on the walls. This model simulated the operation of the 100-kW-class thruster at discharge current ranging from 6 to 10 kA with argon propellant. The extended model reproduced the discharge voltages and wall heat load which are consistent with past experimental results. In addition, the simulation results indicated that cathode sheath voltages account for approximately 5-7 V subject to approximately 20 V of discharge voltages applied between the electrodes. This work was supported by JSPS KAKENHI Grant Numbers 26289328 and 15J10821.

  12. A ferrite core/metallic sheath thermoseed for interstitial thermal therapies.

    PubMed

    Cetas, T C; Gross, E J; Contractor, Y

    1998-01-01

    An alternative form of ferromagnetic seed for thermal therapy has been developed following Matsuki, Murakami, and their colleagues [1]-[4]. A nearly lossless ceramic ferrite core (FC) is surrounded by an electrically conductive sheath. The FC has a high relative intrinsic permeability, typically 3000 at low magnetic field strengths, and a sharp transition from the ferrimagnetic state to the nonmagnetic state. The sheath is either a metallic tube or coating on the core. When this composite seed is excited with a radiofrequency magnetic field, large eddy currents are induced in the metallic sheath (MS) due to the concentrated magnetic flux in the core leading to Joule heating. Advantages of this configuration are that this ferrite core/metallic sheath (FC/MS) thermoseed has high power absorption efficiency and a sharp transition compared to ferromagnetic alloy systems; means of optimizing efficiency are apparent from simple expressions; the outer sheath can be of any biocompatible metal; the production method for the ferrites leads to large quantities of seeds with reproducible properties. The FC/MS configuration solves many of the technical problems that have hindered the clinical implementation of thermally regulating ferromagnetic implants for thermal therapies.

  13. Photoreduction and Oxidation of Cytochrome f in Bundle Sheath Cells of Maize

    PubMed Central

    Bishop, D. G.; Andersen, Kirsten S.; Smillie, Robert M.

    1972-01-01

    The photo-oxidation of cytochrome f (cytochrome c554) in bundle sheath cells isolated from leaves of maize (Zea mays var. DS 606A) has been compared with that in intact maize leaf and in isolated pea leaf cells (Pisum sativum L.). In all cases, illumination with red light caused a negative absorbance change at 554 nm which was attributed to the oxidation of cytochrome f. The extent of this change was greater using monochromatic red light at wavelengths above 700 nm compared with wavelengths below 700 nm. 3-(3,4-Dichlorophenyl)-1, 1-dimethylurea abolished this difference in bundle sheath cells. After illumination for 1 minute or longer in bundle sheath cells, reduction of cytochrome f in the dark was rapid only if the wavelength of the illuminating light was below 700 nm. In the presence of 3-(3,4-dichlorophenyl)-1, 1-dimethlyurea, reduction was slow after illumination at all wavelengths. Cytochrome f photo-oxidation was also followed in cells of a mutant of Chlamydomonas reinhardi, ac-21, which has isolated chloroplasts that exhibit photochemical reactions similar to those shown by isolated bundle sheath chloroplasts. No evidence was obtained for photoreduction of cytochrome f in the mutant. It was concluded that in the chloroplast of the intact bundle sheath cell of maize there is electron flow between photosystem II and cytochrome f resulting in photoreduction of the cytochrome. PMID:16657985

  14. The quantitative role of flexor sheath incision in correcting Dupuytren proximal interphalangeal joint contractures.

    PubMed

    Blazar, P E; Floyd, E W; Earp, B E

    2016-07-01

    Controversy exists regarding intra-operative treatment of residual proximal interphalangeal joint contractures after Dupuytren's fasciectomy. We test the hypothesis that a simple release of the digital flexor sheath can correct residual fixed flexion contracture after subtotal fasciectomy. We prospectively enrolled 19 patients (22 digits) with Dupuytren's contracture of the proximal interphalangeal joint. The average pre-operative extension deficit of the proximal interphalangeal joints was 58° (range 30-90). The flexion contracture of the joint was corrected to an average of 28° after fasciectomy. In most digits (20 of 21), subsequent incision of the flexor sheath further corrected the contracture by an average of 23°, resulting in correction to an average flexion contracture of 4.7° (range 0-40). Our results support that contracture of the tendon sheath is a contributor to Dupuytren's contracture of the joint and that sheath release is a simple, low morbidity addition to correct Dupuytren's contractures of the proximal interphalangeal joint. Additional release of the proximal interphalangeal joint after fasciectomy, after release of the flexor sheath, is not necessary in many patients. IV (Case Series, Therapeutic). © The Author(s) 2015.

  15. Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling

    NASA Astrophysics Data System (ADS)

    Jacquot, Jonathan; Milanesio, Daniele; Colas, Laurent; Corre, Yann; Goniche, Marc; Gunn, Jamie; Heuraux, Stéphane; Kubic, Martin

    2014-02-01

    During the 2011 experimental campaign, one of the three ion cyclotron resonance heating (ICRH) antennas in the Tore Supra (TS) tokamak was equipped with a new type of Faraday screen (FS). The new design aimed at minimizing RF sheaths as well as increasing the heat exhaust capability of the actively cooled screen. It proved to be inefficient for attenuating the RF-sheaths on the screen itself on the contrary to the heat exhaust concept that allowed operation despite higher heat fluxes on the antenna. In parallel, a new approach has been proposed to model self-consistently RF sheaths: the SSWICH (Self-consistent Sheaths and Waves for IC Heating) code. Simulations results from SSWICH coupled with the TOPICA antenna code were able to reproduce the difference between the two FS designs and part of the spatial pattern of heat loads and floating potential. The poloidal pattern is a reliable result that mainly depends on the electrical design of the antenna while the radial pattern is on the contrary highly sensitive to loosely constrained parameters such as perpendicular conductivity that generates a DC current circulation from the the private region inside the antenna limiters to the free SOL outside these limiters. Moreover the cantilevered bars seem to be the element in the design of the new screen that enhanced RF sheaths.

  16. Time-varying impedance of the sheath on a probe in an RF plasma

    NASA Astrophysics Data System (ADS)

    Chen, Francis F.

    2006-11-01

    Langmuir probes used in radiofrequency (rf) discharges usually include compensation elements that minimize the effect of high frequency oscillations in plasma potential. The design of these elements requires knowledge of the capacitance of the sheath on the probe tip, a quantity which varies nonlinearly during the rf cycle. Sheath capacitance has been studied previously for capacitively coupled discharges, where the rf is applied to the electrodes. Here the problem is treated from the standpoint of a small probe in a fluctuating discharge. This work differs from existing literature in that (a) no step model is used and the Debye sheath is treated exactly, (b) the treatment is simple and analytic, (c) the time-variation of the capacitance is explicitly shown, (d) the results are applied to probe design and (e) cylindrical geometry is considered. The rf frequency is assumed low enough that electron transit times can be ignored. We find that when the rf excursions bring the sheath from the Child-Langmuir region into the Debye sheath or electron saturation region, its capacitance has a strongly non-linear behaviour.

  17. Sheath structure in plasma with two species of positive ions and secondary electrons

    NASA Astrophysics Data System (ADS)

    Xiao-Yun, Zhao; Nong, Xiang; Jing, Ou; De-Hui, Li; Bin-Bin, Lin

    2016-02-01

    The properties of a collisionless plasma sheath are investigated by using a fluid model in which two species of positive ions and secondary electrons are taken into account. It is shown that the positive ion speeds at the sheath edge increase with secondary electron emission (SEE) coefficient, and the sheath structure is affected by the interplay between the two species of positive ions and secondary electrons. The critical SEE coefficients and the sheath widths depend strongly on the positive ion charge number, mass and concentration in the cases with and without SEE. In addition, ion kinetic energy flux to the wall and the impact of positive ion species on secondary electron density at the sheath edge are also discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11475220 and 11405208), the Program of Fusion Reactor Physics and Digital Tokamak with the CAS “One-Three-Five” Strategic Planning, the National ITER Program of China (Grant No. 2015GB101003), and the Higher Education Natural Science Research Project of Anhui Province, China (Grant No. 2015KJ009).

  18. Effects of neutral gas collisions on the power transmission factor at the divertor sheath

    NASA Astrophysics Data System (ADS)

    Futch, A. H.; Hill, D. N.; Jong, R. A.; Porter, G. D.; Matthews, G. F.; Buchenauer, D.

    1992-03-01

    We show that charge-exchange and other ion-neutral collisions can reduce the power transmission factor of the plasma sheath, thereby lowering the ion impact energy and target plate sputtering. The power transmission factor relates the heat flux reaching the divertor target to the surface: Delta= Q(sub surf)/n(sub e)T(sub e)C(sub s). Experimental data from the D3-D tokamak suggest that Delta could be as low as 2-3 near the region of peak divertor particle flux, instead of the 7-8 expected from usual sheath theory. Several effects combine to allow ion-neutral interactions to be important in the divertor plasma sheath. The shallow angle of incidence of the magnetic field (1-3 degrees in D3-D) leads to the spatial extension of the sheath from approximately (pi)i approximately = 1 mm normal to the plate to several centimeters along the field lines. Ionization reduces the sheath potential, and collisions reduce the ion impact energy.

  19. Elongation growth of the leaf sheath base of Avena sativa seedlings: regulation by hormones and sucrose

    NASA Technical Reports Server (NTRS)

    Brock, T. G.; Kaufman, P. B.

    1991-01-01

    The leaf sheath base of the seedling of Avena sativa was characterized for growth response to hormones and sucrose. Six day old plants, raised under a 10:14 hr light:dark cycle, were excised at the coleoptilar node and 1 cm above the node for treatment. The growth of the leaf sheath base was promoted by gibberellic acid (GA3) and this response was dose dependent. The lag to response initiation was approximately 4 hr. Growth with or without GA3 (10 micromoles) was transient, diminishing appreciably after 48 hr. The addition of 10 mM sucrose greatly prolonged growth; the effect of GA3 and sucrose was additive. Neither indole-3-acetic acid (IAA) nor the cytokinin N6-benzyladenine (BA), alone or in combination, promoted the growth of leaf sheath bases. However, both significantly inhibited the action of GA3. The inhibitory effect of IAA was dose dependent and was not affected by the addition of BA or sucrose. These results indicate that the growth of leaf sheath bases of Avena sativa is promoted specifically by gibberellin, that this action depends on the availability of carbohydrates from outside of the leaf sheath base, and that the promotional effect of GA3 can be modified by either auxins or cytokinins.

  20. A Rare Malignant Peripheral Nerve Sheath Tumor of the Maxilla Mimicking a Periapical Lesion

    PubMed Central

    Álvares, Pamella; Silva, Luciano; Pereira dos Santos Neto, Alexandrino; Rodrigues, Cleomar Donizeth; Caubi, Antônio; Silveira, Marcia; Sayão, Sandra; Sobral, Ana Paula

    2016-01-01

    Malignant peripheral nerve sheath tumor is a malignant neoplasm that is rarely found in the oral cavity. About 50% of this tumor occurs in patients with neurofibromatosis type I and comprises approximately 10% of all soft tissue sarcomas of head and neck region. Intraosseous malignant peripheral nerve sheath tumor of the maxilla is rare. This article is the first to address malignant peripheral nerve sheath tumor of the maxilla presenting as a periapical radiolucency on nonvital endodontically treated teeth in the English medical literature. Surgical approaches to malignant soft tissue tumor vary based on the extent of the disease, age of the patient, and pathological findings. A rare case of intraosseous malignant peripheral nerve sheath tumor is reported in a 16-year-old woman. The patient presented clinically with a pain involving the upper left incisors region and with defined unilocular periapical radiolucency lesion involved between the upper left incisors. An incisional biopsy was made. Histological and immunohistochemical examination were positive for S-100 protein and glial fibrillary acidic protein showed that the lesion was an intraosseous malignant peripheral nerve sheath tumor of the maxilla. Nine years after the surgery, no regional recurrence was observed. PMID:27994888

  1. A different way of looking at the Plasma-Sheath Boundary Region

    NASA Astrophysics Data System (ADS)

    Franklin, Raoul

    2003-10-01

    The plasma-sheath boundary region has been the subject of study for eighty years, but there are aspects that are still not well understood. At low pressures it is clear that the structure is - plasma-transition layer-thin electron sheath -(thick)ion sheath, and at high pressures it is plasma-collisional sheath, without the need to introduce further structure. As the plasma becomes collisional, there is a question as to how long it is appropriate to speak in terms of the Bohm criterion. Furthermore if the sheath is many ion mean free paths long, the ions may be brought back into collisional equilibrium with the electric field, even though their speed exceeds the ion sound speed of the plasma from which they derive. We examine computationally this intermediate pressure region in terms of how to describe the ion motion, showing how the two limits go over from the one to the other. Most practical gas discharge plasmas are in such a transitional pressure region.

  2. Structural analysis of sheath folds in the Sylacauga Marble Group, Talladega slate belt, southern Appalachians

    USGS Publications Warehouse

    Mies, J.W.

    1993-01-01

    Remnant blocks of marble from the Moretti-Harrah dimension-stone quarry provide excellent exposure of meter-scale sheath folds. Tubular structures with elliptical cross-sections (4 ???Ryz ??? 5) are the most common expression of the folds. The tubes are elongate subparallel to stretching lineation and are defined by centimeter-scale layers of schist. Eccentrically nested elliptical patterns and opposing asymmetry of folds ('S' and 'Z') are consistent with the sheath-fold interpretation. Sheath folds are locally numerous in the Moretti-Harrah quarry but are not widely distributed in the Sylacauga Marble Group; reconnaissance in neighboring quarries provided no additional observations. The presence of sheath folds in part of the Talladega slate belt indicates a local history of plastic, non-coaxial deformation. Such a history of deformation is substantiated by petrographic study of an extracted hinge from the Moretti-Harrah quarry. The sheath folds are modeled as due to passive amplification of initial structures during simple shear, using both analytic geometry and graphic simulation. As indicated by these models, relatively large shear strains (y ??? 9) and longitudinal initial structures are required. The shear strain presumably relates to NW-directed displacement of overlying crystalline rocks during late Paleozoic orogeny. ?? 1993.

  3. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    SciTech Connect

    Křivská, A.; Colas, L.; Milanesio, D.

    2015-12-10

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  4. Biomechanics of the Optic Nerve Sheath in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Ethier, C. Ross; Raykin, Julia; Gleason, Rudy; Mulugeta, Lealem; Myers, Jerry; Nelson, Emily; Samuels, Brian C.

    2014-01-01

    Long-duration space flight carries the risk of developing Visual Impairment and Intracranial Pressure (VIIP) syndrome, a spectrum of ophthalmic changes including posterior globe flattening, choroidal folds, distension of the optic nerve sheath (ONS), optic nerve kinking and potentially permanent degradation of visual function. The slow onset of VIIP, its chronic nature, and certain clinical features strongly suggest that biomechanical factors acting on the ONS play a role in VIIP. Here we measure several relevant ONS properties needed to model VIIP biomechanics. The ONS (meninges) of fresh porcine eyes (n7) was reflected, the nerve proper was truncated near the sclera, and the meninges were repositioned to create a hollow cylinder of meningeal connective tissue attached to the posterior sclera. The distal end was cannulated, sealed, and pressure clamped (mimicking cerebrospinal fluid [CSF] pressure), while the eye was also cannulated for independent control of intraocular pressure (IOP). The meninges were inflated (CSF pressure cycling 7-50 mmHg) while ONS outer diameter was imaged. In another set of experiments (n4), fluid permeation rate across the meninges was recorded by observing the drainage of an elevated fluid reservoir (30 mmHg) connected to the meninges. The ONS showed behavior typical of soft tissues: viscoelasticity, with hysteresis in early preconditioning cycles and repeatable behavior after 4 cycles, and nonlinear stiffening, particularly at CSF pressures 15 mmHg (Figure). Tangent moduli measured from the loading curve were 372 101, 1199 358, and 2050 379 kPa (mean SEM) at CSF pressures of 7, 15 and 30 mmHg, respectively. Flow rate measurements through the intact meninges at 30mmHg gave a permeability of 1.34 0.46 lmincm2mmHg (mean SEM). The ONS is a tough, strain-stiffening connective tissue that is surprisingly permeable. The latter observation suggests that there could be significant CSF drainage through the ONS into the orbit, likely important

  5. Optic Nerve Sheath Mechanics and Permeability in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Best, Lauren; Gleason, Rudy; Mulugeta, Lealem; Myers, Jerry; Nelson, Emily; Samuels, Brian C.; Ethier, C. R.

    2014-01-01

    Long-duration space flight carries the risk of developing Visual Impairment and Intracranial Pressure (VIIP) syndrome, a spectrum of ophthalmic changes including posterior globe flattening, choroidal folds, distension of the optic nerve sheath (ONS), optic nerve kinking and potentially permanent degradation of visual function. The slow onset of VIIP, its chronic nature, and certain clinical features strongly suggest that biomechanical factors acting on the ONS play a role in VIIP. Here we measure several relevant ONS properties needed to model VIIP biomechanics. The ONS (meninges) of fresh porcine eyes (n7) was reflected, the nerve proper was truncated near the sclera, and the meninges were repositioned to create a hollow cylinder of meningeal connective tissue attached to the posterior sclera. The distal end was cannulated, sealed, and pressure clamped (mimicking cerebrospinal fluid [CSF] pressure), while the eye was also cannulated for independent control of intraocular pressure (IOP). The meninges were inflated (CSF pressure cycling 7-50 mmHg) while ONS outer diameter was imaged. In another set of experiments (n4), fluid permeation rate across the meninges was recorded by observing the drainage of an elevated fluid reservoir (30 mmHg) connected to the meninges. The ONS showed behavior typical of soft tissues: viscoelasticity, with hysteresis in early preconditioning cycles and repeatable behavior after 4 cycles, and nonlinear stiffening, particularly at CSF pressures 15 mmHg (Figure). Tangent moduli measured from the loading curve were 372 101, 1199 358, and 2050 379 kPa (mean SEM) at CSF pressures of 7, 15 and 30 mmHg, respectively. Flow rate measurements through the intact meninges at 30mmHg gave a permeability of 1.34 0.46 lmincm2mmHg (mean SEM). The ONS is a tough, strain-stiffening connective tissue that is surprisingly permeable. The latter observation suggests that there could be significant CSF drainage through the ONS into the orbit, likely important

  6. Staged image guided robotic radiosurgery for optic nerve sheath meningiomas.

    PubMed

    Romanelli, Pantaleo; Bianchi, Livia; Muacevic, Alexander; Beltramo, Giancarlo

    2011-01-01

    Optic nerve sheath meningiomas (ONSMs) represent the most challenging lesions involving the optic pathways: Microsurgery is not indicated and classical single-stage radiosurgery appears to be too risky due to the expected destruction of the common blood supply with consequent loss of vision. Staged radiosurgery might be one treatment option because it exploits the ability of normal tissues to repair sub-lethal radiation-induced damage, offering a chance to control tumor growth while sparing function. Staged robotic radiosurgery was offered to 5 patients harboring ONSMs with the aim of sparing vision while achieving local growth control. Five patients with ONSM presenting with visual field deficits and loss of visual acuity were treated with staged CyberKnife radiosurgery, receiving 20 Gy in 4 stages (5 Gy per stage). Treatment planning was based on contrast-enhanced thin-slice CT (1.25 mm thickness for the first three cases, 0.5 mm for the last two) and volumetric MR imaging (1.5 T for the first three cases, 3 T for the last two). An interval of 24 hours was strictly observed between stages. Visual acuity and visual fields were assessed in all patients immediately prior to treatment and at intervals of 6 months thereafter. Follow-up MRIs were performed every 6 months for 2 years, then once per year. The entire procedure, inclusive of imaging, treatment planning and treatment delivery, was performed in 5 days. Irradiation required approximately 45 min per stage. Mean tumor volume was 2.94 cc (range: 0.8-6.4 cc). Treatment was well tolerated in all patients. Follow-up ranged from 36 to 74 months. Local growth control was achieved in all patients. Restoration of normal vision was experienced by 4 patients 6 to 12 months after the treatment. One patient, who was also affected by diabetic retinopathy, showed a modest improvement after 6 months, remaining stable thereafter. Staged CyberKnife radiosurgery provides a fast and well-tolerated non

  7. Role of disulfide bonds in maintaining the structural integrity of the sheath of Leptothrix discophora SP-6.

    PubMed Central

    Emerson, D; Ghiorse, W C

    1993-01-01

    Isolated sheaths of Leptothrix discophora SP-6 (ATCC 51168) were tested for susceptibility to degradation by a variety of chemical denaturants and lytic enzymes and found to be resistant to many reagents and enzyme treatments. However, disulfide bond-reducing agents such as dithiothreitol (DTT), beta-mercaptoethanol, sodium cyanide, and sodium sulfite degraded the sheath, especially at elevated pH (pH 9) and temperature (50 degrees C). DTT and beta-mercaptoethanol caused more rapid degradation of the sheath than cyanide or sulfite. Treatment of the sheath with 1 N NaOH resulted in rapid breakdown, while treatment with 1 N HCl resulted in slow but significant hydrolysis. Transmission electron microscopy showed that the 6.5-nm fibrils previously shown to be an integral structural element of the sheath fabric (D. Emerson and W. C. Ghiorse, J. Bacteriol. 175:7808-7818, 1993) were progressively dissociated into random masses during DTT-induced degradation. Quantitation of disulfide bonds with DTT showed that the sheaths contained approximately 2.2 mumol of disulfides per mg of sheath protein. Reaction with 5,5'-dithio-bis-(2-nitrobenzoic acid) showed that sheaths also contained approximately 0.8 mumol of free sulfhydryls per mg of protein. A sulfhydryl-specific fluorescent probe (fluorescein 5-maleimide) showed that the free sulfhydryls in sheathed cell filaments were evenly distributed throughout the sheath. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis autoradiography of [14C]iodoacetamide-labeled sheaths and DTT-dissociated sheath fibril suspensions showed that the majority of 14C-labeled sulfhydryls in the sheaths did not enter the gel. However, low-molecular-mass silver-staining bands (14 to 45 kDa) did appear in the gels after iodoacetic acid or iodoacetamide alkylation of the dissociated fibrils. These bands did not stain with Coomassie blue. Their migration in gels was slightly affected by digestion with pronase. The fibrils contained 20 to 25

  8. Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster

    SciTech Connect

    Zhang, Fengkui Kong, Lingyi; Li, Chenliang; Yang, Haiwei; Li, Wei

    2014-11-15

    Despite its affordability, the krypton Hall-effect thruster in applications always had problems in regard to performance. The reason for this degradation is studied from the perspective of the near-wall conductivity of electrons. Using the particle-in-cell method, the sheath oscillation characteristics and its effect on near-wall conduction are compared in the krypton and xenon Hall-effect thrusters both with wall material composed of BNSiO{sub 2}. Comparing these two thrusters, the sheath in the krypton-plasma thruster will oscillate at low electron temperatures. The near-wall conduction current is only produced by collisions between electrons and wall, thereby causing a deficiency in the channel current. The sheath displays spatial oscillations only at high electron temperature; electrons are then reflected to produce the non-oscillation conduction current needed for the krypton-plasma thruster. However, it is accompanied with intensified oscillations.

  9. Sheath effects observed on a 10 meter high voltage panel in simulated low earth orbit plasma

    NASA Technical Reports Server (NTRS)

    Mccox, J. E.; Konradi, A.

    1979-01-01

    A large (1m x 10m) flat surface of conductive material was biased to high voltage (+ or - 3000 V) to simulate the behavior of a large solar array in low earth orbit. The model array was operated in a plasma environment of 1,000 to 1,000,000/cu cm, with sufficient free space around it for the resulting plasma sheaths to develop unimpeded for 5-10 meters into the surrounding plasma. Measurements of the resulting sheath thickness were obtained. The observed thickness varied approximately as V to the 3/4 power and N to the 1/2 power. This effect appears to limit total current leakage from the test array until sheath dimensions exceed about 1 meter. Total leakage current was also measured with the array.

  10. A matching approach to communicate through the plasma sheath surrounding a hypersonic vehicle

    SciTech Connect

    Gao, Xiaotian; Jiang, Binhao

    2015-06-21

    In order to overcome the communication blackout problem suffered by hypersonic vehicles, a matching approach has been proposed for the first time in this paper. It utilizes a double-positive (DPS) material layer surrounding a hypersonic vehicle antenna to match with the plasma sheath enclosing the vehicle. Analytical analysis and numerical results indicate a resonance between the matched layer and the plasma sheath will be formed to mitigate the blackout problem in some conditions. The calculated results present a perfect radiated performance of the antenna, when the match is exactly built between these two layers. The effects of the parameters of the plasma sheath have been researched by numerical methods. Based on these results, the proposed approach is easier to realize and more flexible to the varying radiated conditions in hypersonic flight comparing with other methods.

  11. Sheath effects observed on a 10 meter high voltage panel in simulated low earth orbit plasma

    NASA Technical Reports Server (NTRS)

    Mccox, J. E.; Konradi, A.

    1979-01-01

    A large (1m x 10m) flat surface of conductive material was biased to high voltage (+ or - 3000 V) to simulate the behavior of a large solar array in low earth orbit. The model array was operated in a plasma environment of 1,000 to 1,000,000/cu cm, with sufficient free space around it for the resulting plasma sheaths to develop unimpeded for 5-10 meters into the surrounding plasma. Measurements of the resulting sheath thickness were obtained. The observed thickness varied approximately as V to the 3/4 power and N to the 1/2 power. This effect appears to limit total current leakage from the test array until sheath dimensions exceed about 1 meter. Total leakage current was also measured with the array.

  12. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles

    NASA Astrophysics Data System (ADS)

    Liu, Z. F.; Fang, S.; Moura, F. A.; Ding, J. N.; Jiang, N.; Di, J.; Zhang, M.; Lepró, X.; Galvão, D. S.; Haines, C. S.; Yuan, N. Y.; Yin, S. G.; Lee, D. W.; Wang, R.; Wang, H. Y.; Lv, W.; Dong, C.; Zhang, R. C.; Chen, M. J.; Yin, Q.; Chong, Y. T.; Zhang, R.; Wang, X.; Lima, M. D.; Ovalle-Robles, R.; Qian, D.; Lu, H.; Baughman, R. H.

    2015-07-01

    Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation and electronic properties.

  13. Leptothrix sp. sheaths modified with iron oxide particles: Magnetically responsive, high aspect ratio functional material.

    PubMed

    Safarik, Ivo; Angelova, Ralitsa; Baldikova, Eva; Pospiskova, Kristyna; Safarikova, Mirka

    2017-02-01

    Smart materials of biological origin are attracting a lot of attention nowadays, especially as catalysts, carriers or adsorbents. Among them, magnetically modified biomaterials are especially important due to their response to external magnetic field. This report demonstrates that naturally occurring micrometer sized, high aspect ratio material (native and autoclaved Leptothrix sp. sheaths) efficiently bind synthetically prepared magnetite and maghemite nanoparticles and their aggregates. Magnetic modification of Leptothrix sheaths enables to prepare a promising material for advanced biotechnology and environmental technology applications. The prepared magnetically responsive sheaths were tested as inexpensive adsorbent for crystal violet removal from aqueous solutions. The observed maximum adsorption capacity was 243.1mg of dye per 1g of adsorbent. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Observation of Self-Sustaining Relativistic Ionization Wave Launched by a Sheath Field

    NASA Astrophysics Data System (ADS)

    McCormick, M.; Arefiev, A. V.; Quevedo, H. J.; Bengtson, R. D.; Ditmire, T.

    2014-01-01

    We present experimental evidence supported by simulations of a relativistic ionization wave launched into a surrounding gas by the sheath field of a plasma filament with high energy electrons. Such a filament is created by irradiating a clustering gas jet with a short pulse laser (115 fs) at a peak intensity of 5×1017 W/cm2. We observe an ionization wave propagating radially through the gas for about 2 ps at 0.2-0.5 c after the laser has passed, doubling the initial radius of the filament. The gas is ionized by the sheath field, while the longevity of the wave is explained by a moving field structure that traps the high energy electrons near the boundary, maintaining a strong sheath field despite the significant expansion of the plasma.

  15. A matching approach to communicate through the plasma sheath surrounding a hypersonic vehicle

    NASA Astrophysics Data System (ADS)

    Gao, Xiaotian; Jiang, Binhao

    2015-06-01

    In order to overcome the communication blackout problem suffered by hypersonic vehicles, a matching approach has been proposed for the first time in this paper. It utilizes a double-positive (DPS) material layer surrounding a hypersonic vehicle antenna to match with the plasma sheath enclosing the vehicle. Analytical analysis and numerical results indicate a resonance between the matched layer and the plasma sheath will be formed to mitigate the blackout problem in some conditions. The calculated results present a perfect radiated performance of the antenna, when the match is exactly built between these two layers. The effects of the parameters of the plasma sheath have been researched by numerical methods. Based on these results, the proposed approach is easier to realize and more flexible to the varying radiated conditions in hypersonic flight comparing with other methods.

  16. Linkage between gravity perception and response in the grass leaf-sheath pulvinus

    NASA Technical Reports Server (NTRS)

    Dayanandan, P.; Franklin, C. I.; Kaufman, P. B.

    1982-01-01

    Cellulose synthesis inhibitors 2,6-dichlorobenzonitrile and coumarin inhibit the normal gravitropic response of the leaf-sheath pulvini in several grasses. These inhibitors induce thickenings that are mostly distributed in the radial walls. Their distribution patterns follow a previously published equation that describes the geometry of asymmetric growth in the leaf-sheath pulvinus. It is proposed that radial transport of growth promotors may account for the observed asymmetric growth rather than the classical concept of lateral downward transport in an horizontally placed shoot. Electron microscopic observation of an interaction between the tonoplast membrane and statoliths suggests that such an interaction might be a basis for gravity perception in grass leaf-sheath pulvini.

  17. The arterial blood supply for the synovial tendon sheaths of the hand.

    PubMed

    de la Garza, Oscar; Lierse, Werner; de los Angeles-García, Ma; Elizondo, Rodrigo; Guzmán, Santos

    2008-01-01

    The blood supply for the synovial tendon sheaths of the hand was carefully investigated. We show that the origin of those arteries, supplying the synovial tendon-sheaths of the Mm. flexor pollicis longus, flexor digitorum superficialis and profundus, lies in the Canalis carpi. We also describe that the branches of the Aa. digitales palmares propriae arise independently. We emphasize that the terminal branches of the A. interossea posterior and the Rete carpi dorsalis form an arterial network on the synovial tendon sheaths of the Dorsum manus. The synovial membranes of the proximal joints of the fingers receive an ample blood supply from the Rami ascendentes of the Aa. metacarpeae palmares and the Aa. digitales palmares propriae (Aa. recurrentes).

  18. Unified model of the rf plasma sheath: Part 2, Asymptotic connection formulae

    SciTech Connect

    Riley, M.E.

    1996-08-01

    A previously-developed approximation to the first integral of the Poisson equation enables one to obtain solutions for the voltage- current characteristics of a radio-frequency (rf) plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current-specified conditions. The theory reproduced the time-dependent voltage-current characteristics of the two extreme cases corresponding to the Lieberman rf sheath theory and the Metze-Ernie-Oskam theory. In this paper the sheath model is connected to the plasma bulk description, and a prescription is given for the ion relaxation time constant, which determines the time-dependent ion impact energy on the electrode surface. It appears that this connected model should be applicable to those high density, low pressure plasmas in which the Debye length is a small fraction of the ion mean free path, which itself is a small fraction of the plasma dimension.

  19. Motile tubular vacuoles in extramatrical mycelium and sheath hyphae of ectomycorrhizal systems.

    PubMed

    Allaway, W G; Ashford, A E

    2001-01-01

    Extramatrical mycelium and outer hyphae of the sheath of Eucalyptus pilularis-Pisolithus tinctorius mycorrhizas contain abundant motile tubular vacuoles which accumulate the carboxyfluorescein analogue Oregon Green 488 carboxylic acid. The fluorochrome accumulates in a system of small vacuoles, tubules, and larger vacuoles, which are interlinked, motile, and pleiomorphic, in external hyphae, cords, and hyphae of the outer sheath. There is often a difference in fluorescence between two neighbouring cells, indicating that the dolipore septum exercises control on the movement of material between cells. Generally the motile tubular vacuole system in mycorrhizas resembles that previously found in isolated mycelium. The majority of fungal cells in the sheath contain no fluorochrome even after long exposure of the mycorrhiza to the solution, but with differential interference optics the cells are clearly seen to be alive and to contain vacuoles resembling those in the outer hyphae. In translocation experiments, long-distance transport of the fluorochrome is slow and slight, or even nonexistent in some cases.

  20. Linkage between gravity perception and response in the grass leaf-sheath pulvinus

    NASA Technical Reports Server (NTRS)

    Dayanandan, P.; Franklin, C. I.; Kaufman, P. B.

    1982-01-01

    Cellulose synthesis inhibitors 2,6-dichlorobenzonitrile and coumarin inhibit the normal gravitropic response of the leaf-sheath pulvini in several grasses. These inhibitors induce thickenings that are mostly distributed in the radial walls. Their distribution patterns follow a previously published equation that describes the geometry of asymmetric growth in the leaf-sheath pulvinus. It is proposed that radial transport of growth promotors may account for the observed asymmetric growth rather than the classical concept of lateral downward transport in an horizontally placed shoot. Electron microscopic observation of an interaction between the tonoplast membrane and statoliths suggests that such an interaction might be a basis for gravity perception in grass leaf-sheath pulvini.

  1. Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

    SciTech Connect

    Douglass, Angela; Land, Victor; Qiao Ke; Matthews, Lorin; Hyde, Truell

    2012-01-15

    Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a radio frequency plasma discharge by changing the discharge power. The trajectories of particles dropped from the top of the discharge chamber are used to reconstruct the vertical electric force acting on the particles. The resulting data, together with the results from a self-consistent fluid model, are used to determine the lower levitation limit for dust particles in the discharge and the approximate height above the lower electrode where quasineutrality is attained, locating the sheath edge. These results are then compared with current sheath models. It is also shown that particles levitated within a few electron Debye lengths of the sheath edge are located outside the linearly increasing portion of the electric field.

  2. Synthesis and interface structures of zinc sulfide sheathed zinc-cadmium nanowire heterojunctions.

    PubMed

    Shen, Guozhen; Bando, Yoshio; Gao, Yihua; Golberg, Dmitri

    2006-07-27

    Zinc sulfide (ZnS) sheathed zinc (Zn)-cadmium (Cd) nanowire heterojunctions have been prepared by thermal evaporating of ZnS and CdS powders in a vertical induction furnace at 1200 degrees C. Studies found that both the Zn and Cd subnanowires, within a single nanoheterojunction, are single-crystallines with the growth directions perpendicular to the [210] plane, whereas the sheathed ZnS is polycrystalline with a thickness of ca. 5 nm. The Zn/Cd interface structure in the ZnS sheathed Zn-Cd nanowire heterojunctions was thoroughly experimentally studied by high-resolution transmission electron microscopy and theoretically studied using a near-coincidence site lattice (NCSL) concept. The results show that the Cd and Zn have a crystalline orientation relationship as [0001]Zn//[0001]Cd, (10(-)10)Zn//(10(-)10)Cd, (01(-)10)Zn//(01(-)10)Cd, and ((-)1100)Zn//((-)1100)Cd.

  3. Magnetic Field Generation in Core-sheath Jets via the Kinetic Kelvin-Helmholtz Instability

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Hardee, P. E.; Duţan, I.; Niemiec, J.; Medvedev, M.; Mizuno, Y.; Meli, A.; Sol, H.; Zhang, B.; Pohl, M.; Hartmann, D. H.

    2014-09-01

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.

  4. Measurements of the asymmetric, dynamic sheath around a pulse biased sphere immersed in flowing metal plasma

    SciTech Connect

    Anders, Andre; Wu, Hongchen; Anders, Andre

    2008-06-13

    A long-probe technique was utilized to record the expansion and retreat of the dynamic sheath around a spherical substrate immersed in pulsed cathode arc metal plasma. Positively biased, long cylindrical probes were placed on the side and downstream of a negatively pulsed biased stainless steel sphere of 1" (25.4 mm) diameter. The amplitude and width of the negative high voltage pulses (HVP) were 2 kV, 5 kV, 10 kV, and 2 mu s, 4 mu s, 10 mu s, respectively. The variation of the probe (electron) current during the HVP is a direct measure for the sheath expansion and retreat. Maximum sheath sizes were determined for the different parameters of the HVP. The expected rarefaction zone behind the biased sphere (wake) due to the fast plasma flow was clearly established and quantified.

  5. Electromagnetic particle in cell modeling of the plasma focus: Current sheath formation and lift off

    SciTech Connect

    Seng, Y. S.; Lee, P.; Rawat, R. S.

    2014-02-15

    The shaping and formation of the current sheath takes place in the breakdown phase of a plasma focus device and critically controls the device performance. Electrostatic particle in cell codes, with magnetic effects ignored, have been used to model the breakdown phase. This Letter reports the successful development and implementation of an electromagnetic particle in cell (EMPIC) code, including magnetic effects self-consistently, to simulate the breakdown phase; from the ionization, localization and gliding discharge along the insulator to the time instant of current sheath lift off. The magnetic field was found to be appreciable from the time the current sheath came into contact with the anode with increased local current, initiating the voltage breakdown of the device as a result.

  6. Constrained sheath optics for high thrust density, low specific impulse ion thrusters

    NASA Technical Reports Server (NTRS)

    Wilbur, Paul J.; Han, Jian-Zhang

    1987-01-01

    The results of an experimental study showing that a contoured, fine wire mesh attached to the screen grid can be used to control the divergence characteristics of ion beamlets produced at low net-to-total accelerating voltage ratios are presented. The influence of free and constrained-sheath optics systems on beamlet divergence characteristics are found to be similar in the operating regime investigated, but it was found that constrained-sheath optics systems can be operated at higher perveance levels than free-sheath ones. The concept of a fine wire interference probe that can be used to study ion beamlet focusing behavior is introduced. This probe is used to demonstrate beamlet focusing to a diameter about one hundreth of the screen grid extraction aperture diameter. Additional testing is suggested to define an optimally contoured mesh that could yield well focused beamlets at net-to-total accelerating voltage ratios below about 0.1.

  7. Palliative Epineurotomy for Focal Radial Malignant Peripheral Nerve Sheath Tumor in a Dog.

    PubMed

    Gibson, Andrew David; Davies, Emma; Lara-Garcia, Ana; Lafuente, Pilar

    2016-01-01

    This case report describes the diagnosis of a peripheral nerve sheath tumor of the deep branch of the radial nerve distal to the elbow in a dog. The lesion was identified using computed tomography and ultrasonography and confirmed as sarcoma on histopathological analysis of incisional biopsies. Clinical signs dramatically improved following surgical biopsy before recurring three months later. Repeat epineurotomy of the deep branch of the radial nerve resulted in clinical improvement for a further month before signs once again returned. Epineurotomy as a palliative treatment for peripheral nerve sheath tumors has not been previously described, but may have a place in palliation of clinical signs in specific cases of peripheral nerve sheath tumors in which limb amputation is not an option.

  8. Electromagnetic induction between axons and their schwann cell myelin-protein sheaths.

    PubMed

    Goodman, G; Bercovich, D

    2013-12-01

    Two concepts have long dominated vertebrate nerve electrophysiology: (a) Schwann cell-formed myelin sheaths separated by minute non-myelinated nodal gaps and spiraling around axons of peripheral motor nerves reduce current leakage during propagation of trains of axon action potentials; (b) "jumping" by action potentials between successive nodes greatly increases signal conduction velocity. Long-held and more recent assumptions and issues underlying those concepts have been obscured by research emphasis on axon-sheath biochemical symbiosis and nerve regeneration. We hypothesize: mutual electromagnetic induction in the axon-glial sheath association, is fundamental in signal conduction in peripheral and central myelinated axons, explains the g-ratio and is relevant to animal navigation.

  9. Pyramiding transgenic resistance in elite indica rice cultivars against the sheath blight and bacterial blight.

    PubMed

    Maruthasalam, S; Kalpana, K; Kumar, K K; Loganathan, M; Poovannan, K; Raja, J A J; Kokiladevi, E; Samiyappan, R; Sudhakar, D; Balasubramanian, P

    2007-06-01

    Elite indica rice cultivars were cotransformed with genes expressing a rice chitinase (chi11) and a thaumatin-like protein (tlp) conferring resistance to fungal pathogens and a serine-threonine kinase (Xa21) conferring bacterial blight resistance, through particle bombardment, with a view to pyramiding sheath blight and bacterial blight resistance. Molecular analyses of putative transgenic lines by polymerase chain reaction, Southern Blot hybridization, and Western Blotting revealed stable integration and expression of the transgenes in a few independent transgenic lines. Progeny analyses showed the stable inheritance of transgenes to their progeny. Coexpression of chitinase and thaumatin-like protein in the progenies of a transgenic Pusa Basmati1 line revealed an enhanced resistance to the sheath blight pathogen, Rhizoctonia solani, as compared to that in the lines expressing the individual genes. A transgenic Pusa Basmati1 line pyramided with chi11, tlp, and Xa21 showed an enhanced resistance to both sheath blight and bacterial blight.

  10. Positron acceleration by sheath field in ultra-intense laser–solid interactions

    NASA Astrophysics Data System (ADS)

    Yan, Yonghong; Wu, Yuchi; Chen, Jia; Yu, Minghai; Dong, Kegong; Gu, Yuqiu

    2017-04-01

    A positron production experiment was performed by irradiating an ultra-intense picosecond laser on solid tantalum targets. Quasi-monoenergetic positron beams were obtained owing to the sheath field on the back of the target. The experiment shows that the peak energy of the positron spectrum has a linear relation with the reciprocal of the target diameter. A simple analytical model of the sheath field was constructed to explain the experimental data, which predicts the positron peak energy in terms of the target diameter and hot electron parameters. Based on the field model, Monte Carlo simulations were conducted to treat the positron production and acceleration self-consistently. The simulated spectra are in good agreement with most experiment results. The disagreement of the 1 mm diameter data reveals that the hot electron propagation along the target flank surface plays an important role in the sheath field set up. Several aspects involved in the positron acceleration are discussed.

  11. STRETCHY ELECTRONICS. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles.

    PubMed

    Liu, Z F; Fang, S; Moura, F A; Ding, J N; Jiang, N; Di, J; Zhang, M; Lepró, X; Galvão, D S; Haines, C S; Yuan, N Y; Yin, S G; Lee, D W; Wang, R; Wang, H Y; Lv, W; Dong, C; Zhang, R C; Chen, M J; Yin, Q; Chong, Y T; Zhang, R; Wang, X; Lima, M D; Ovalle-Robles, R; Qian, D; Lu, H; Baughman, R H

    2015-07-24

    Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.

  12. Production of bi-component core-sheath nanofibers using Chitosan and Polyethylene oxide

    NASA Astrophysics Data System (ADS)

    Ojha, Satyajeet; Stevens, Derrick; Clarke, Laura; Gorga, Russell

    2007-03-01

    There has been a renewed interest to develop fibers at nanometer scale due to the large number of potential biomedical uses such as tissue engineering, drug delivery and wound care applications. Chitosan is a naturally occurring polysaccharide obtained from crustaceans. Its antibacterial properties have been acknowledged. Our effort has been to develop core-sheath nanofibers using chitosan, and poly (ethylene oxide) (PEO), another bio-compatible polymer. The critical properties and parameters such as feed rate, electric field, distance between needle and grounded collector and their consequences on morphology are discussed. Chitosan/PEO solutions have been characterized by surface tension, molecular weight and viscosity which are crucial factors to achieve core-sheath geometry. Tensile and conductive properties of these core-sheath nanofibers have been investigated which could be important for them to be used in wound scaffolds and cell-culture respectively.

  13. Confinement and structure of electrostatically coupled dust clouds in a direct current plasma-sheath

    NASA Astrophysics Data System (ADS)

    Nunomura, S.; Ohno, N.; Takamura, S.

    1998-10-01

    Mechanisms for the confinement and the internal structure of an electrostatically coupled dust cloud formed in a dc glow discharge have been investigated from a comparative viewpoint between experimental observations and a simple model. Two kinds of dust clouds with different internal structures are clearly observed, depending on the dispersion of the size distribution of dust particles. The dust cloud can be trapped only in the plasma-sheath boundary area, corresponding to the potential minimum region determined by gravitational and electrostatic forces in the cathode sheath. No dust particles were found deep inside of the sheath, which is consistent with the analysis because the dust particles may be charged positively due to an extreme reduction of the electron density. The internal structure of the electrostatically coupled dust cloud was found to be arranged so that the total potential energy, including the repulsive Coulomb interaction among negative dust particles, may become minimal.

  14. Studies of anode sheath phenomena in a Hall-effect thruster discharge

    NASA Astrophysics Data System (ADS)

    Dorf, Leonid

    2005-10-01

    Crossed electric and magnetic fields devices (plasma thrusters, magnetrons, coaxial plasma guns, plasma opening switches, etc.) are routinely used for plasma production and in other applications. Despite these numerous applications, the fundamental anode sheath phenomena in many of these devices have received surprisingly little experimental scrutiny. We chose a Hall-effect thruster (HT) discharge for our study of the anode sheath. It has been typically assumed in most fluid models of an HT that its steady-state operation requires the presence of a negative anode fall (electron-repelling anode sheath). Such anode fall behavior, opposite to that in typical glow discharges or hollow-anode plasma sources, is the result of a relatively high degree of ionization in HTs, achieved by applying a radial magnetic field transverse to the direction of the discharge current. Our data from non-perturbing probe measurements showed for the first time that the anode fall in HTs can be either negative or positive (electron-attracting anode sheath), depending on conditions at the anode surface. The path for current closure to the anode turns out to be quite subtle in HTs. This path determines the mechanism of the anode fall formation. In varying the magnetic field topology in the channel from a more uniform to a cusp-like one, we uncover intriguing results. For cusp configurations, in which the radial magnetic field changes polarity somewhere along the channel, the anode fall is positive, whereas it is negative for a more uniform field. This polarity difference could be attributed to the decreased electron mobility across the magnetic field in the cusp-like configuration. Our theoretical modeling of the anode sheath correlates well with the experimental results in describing how the magnitude of the sheath varies with the discharge voltage and mass flow rate.

  15. Application of Spray Foam Insulation Under Plywood and Oriented Strand Board Roof Sheathing

    SciTech Connect

    Grin, A.; Smegal, J.; Lstiburek, J.

    2013-10-01

    Unvented roof strategies with open cell and closed cell spray polyurethane foam insulation sprayed to the underside of roof sheathing have been used since the mid-1990's to provide durable and efficient building enclosures. However, there have been isolated moisture related incidents reported anecdotally that raise potential concerns about the overall hygrothermal performance of these systems. The incidents related to rainwater leakage and condensation concerns. Condensation concerns have been extensively studied by others and are not further discussed in this report. This project involved hygrothermal modeling of a range of rainwater leakage and field evaluations of in-service residential roofs using spray foam insulation. All of the roof assemblies modeled exhibited drying capacity to handle minor rainwater leakage. All field evaluation locations of in-service residential roofs had moisture contents well within the safe range for wood-based sheathing. Explorations of eleven in-service roof systems were completed. The exploration involved taking a sample of spray foam from the underside of the roof sheathing, exposing the sheathing, then taking a moisture content reading. All locations had moisture contents well within the safe range for wood-based sheathing. One full-roof failure was reviewed, as an industry partner was involved with replacing structurally failed roof sheathing. In this case the manufacturer's investigation report concluded that the spray foam was installed on wet OSB based on the observation that the spray foam did not adhere well to the substrate and the pore structure of the closed cell spray foam at the ccSPF/OSB interface was indicative of a wet substrate.

  16. A self-consistent hybrid model of a dual frequency sheath: Ion energy and angular distributions

    SciTech Connect

    Dai Zhongling; Xu Xiang; Wang Younian

    2007-01-15

    This paper presents a self-consistent hybrid model including the fluid model which can describe the characteristics of collisional sheaths driven by dual radio-frequency (DF) sources and Monte Carlo (MC) method which can determine the ion energy and angular distributions incident onto the dual rf powered electrode. The charge-exchange collisions between ions and neutrals are included in the MC model in which a self-consistent instantaneous electric field obtained from the fluid model is adopted. In the simulation, the driven method we used is either the current-driven method or the voltage-driven method. In the current-driven method, the rf current sources are assumed to apply to an electrode, which is the so-called the equivalent circuit model and is used to self-consistently determine the relationship between the instantaneous sheath potential and the sheath thickness. In the voltage-driven method, however, the rf voltage sources are assumed to apply to an electrode. The dual rf sheath potential, sheath thickness, ion flux, ion energy distributions (IEDs), and ion angular distributions (IADs) are calculated for different parameters. The numerical solutions show that some external parameters such as the bias frequency and power of the lower-frequency source as well as gas pressure are crucial for determining the structure of collisional dual rf sheaths and the IEDs. The shapes of the IADs, however, are determined mainly by the gas pressure. Furthermore, it is found that the results from the different driven methods behave in the same way although there are some differences in some quantities.

  17. An analysis of the biomechanics of interference screw fixation and sheathed devices for biceps tenodesis.

    PubMed

    Saithna, Adnan; Chizari, Mahmoud; Morris, Guy; Anley, Cameron; Wang, Bin; Snow, Martyn

    2015-07-01

    This study aimed to evaluate the differences in biomechanical properties of biceps tenodesis when performed with sheathed versus unsheathed screws and also to investigate the effect of altering the pre-tension. Tenodesis was performed in an in vitro model using biomechanical test blocks and ovine tendons. Blocks were allocated to 1 of 5 groups which varied by method of tenodesis and cyclical loading protocol: Group A, Biosure PK screw (10-100 N), Group B: 7-8 mm Biosure Sync and Biosure PK screw (10-100 N), Group C: Biosure PK screw (10-70 N), Group D: Biosure PK (20-100 N), and Group E: custom sheath and Biosure PK screw (10-100 N). If tenodeses remained intact after 500 cycles maximum load to failure testing was performed. 30% of tenodeses in Group A failed prior to 500 cycles whereas none failed in the sheathed device groups (P=0.02). Using a sheathed device prevented mal-rotation. However, tenodeses in Group B were more likely to fail immediately distal to the tenodesis at a load below the anticipated maximum load to failure suggesting tendon damage during fixation. Using the custom sheath, which did not have sharp edges, resulted in a statistically significant increased maximum load to failure in Group E (348 N) when compared to Group A (228 N, mean difference 120 N, P=0.01) and Group B (253N, mean difference 95 N, P=0.0007). Sheathed devices prevent mal-rotation and increase stiffness and maximum load to failure. This is further improved by reducing tendon damage at the time of tenodesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Three new techniques for creation of a steerable sheath, a 4F snare, and bidirectional sheath inversion using existing endovascular materials.

    PubMed

    Mallios, Alexandros; Yankovic, Willy; Boura, Benoit; Combes, Myriam

    2012-09-01

    We present three novel techniques for creation of (1) a steerable sheath, (2) a 4F snare device, and (3) dual anterograde and retrograde double-wire percutaneous transluminal angioplasty access technique using a single femoral puncture. These techniques were conceived and bench-tested in our institution, allowing the utilization of inexpensive equipment for complicated endovascular procedures. They offer (1) controlled navigation, no-touch vessel cannulation and cannulation of angulated vessels, contralateral limb of stent grafts, fenestrations, and branches; (2) a low-profile (4F external diameter) modifiable snare with the ability to expand to the size of an entire aneurysm and the ability to undo the snare in case of blockage with other endovascular material; and (3) in situ sheath inversion for concomitant anterograde and retrograde percutaneous angioplasty with a single femoral puncture.

  19. Pre-implantation electrochemical characterization of a Parylene C sheath microelectrode array probe.

    PubMed

    Hara, Seth A; Kim, Brian J; Kuo, Jonathan T W; Lee, Curtis; Gutierrez, Christian A; Hoang, Tuan; Meng, Ellis

    2012-01-01

    We present the preliminary electrochemical characterization of 3D Parylene C sheath microelectrode array probes towards realizing reliable chronic neuroprosthetic recordings. Electrochemical techniques were used to verify electrode integrity after our novel post-fabrication thermoforming process was applied to flat surface micromachined structures to achieve a hollow sheath probe shape. Characterization of subsequent neurotrophic coatings was performed and accelerated life testing was used to simulate six months in vivo. Prior to probe implantation, crosstalk was measured and electrode surface properties were evaluated through the use of electrochemical impedance spectroscopy.

  20. Child-Langmuir law applicability for a cathode sheath description of glow discharge in hydrogen

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V. A.; Artushenko, K. P.; Yegorenkov, V. D.

    2016-08-01

    The present paper reveals that the Child-Langmuir law version with the constant ion mobility has to be applied for the cathode sheath description of the glow discharge in hydrogen. Using the analytical model we demonstrate that even in a high electric field the constant mobility law version rather than that for the constant ion mean free path has to hold in the case of impeded charge exchange and the dominant effect of polarization forces on the ion motion through the cathode sheath.

  1. [Connective tissue reinforcing structures of the digital tendon sheaths of the human hand].

    PubMed

    Knott, C; Schmidt, H M

    1986-01-01

    At a greater number of humid preparated human hands, all the ligamentous supports of the digital tendon sheath were exposed and their dimensions were determined. The osteofibrous channels, which contain the long flexor tendons of the digits, were bounded on the one hand by transversely concave shaft areas of the phalanges and the palmar ligaments and on the other side by the fibrous parts of the tendon sheath. From the second to the 5th finger, it has a regular extension of length, which begins proximal at the heads of the metacarpal bones and runs distal to the base of the nail phalanx. In some cases, there is a continuous communication between the digital tendon sheath of the little finger and the carpal synovial sheath. The tendon sheath of the flexor pollicis longus muscle in comparison with it is always in an open communication with the radial synovial sac of the wrist. At the fibrous supports of the digital tendon sheath, one can find constant and inconstant ligamentous structures. Regular shaped ligaments consist of annular fibers (A1 to A5). The proximal complex of fiber supports is a formation of the A1 and A2 ligaments. The band A1 can be divided into 2 ligaments both of roughly equal length, which lay between the head of the metacarpal bone and the base of the proximal phalanx. The strongest fibrous support of the whole digital tendon sheath represents the band A2. It is attached to the midth of the proximal phalanx and increases in strength from proximal to distal. The middle length varies between 6.7 mm at the thumb and 18.7 mm at the middle finger. The distal margin is strengthened by fibrocartilage tissue to be in accordance with the important function as a pulley. The annular band A4 forms the distal supporting complex height above the shaft of the middle phalanx. At the 2nd to the 5th finger it is, with a middle length of 6 to 7 mm, very much shorter than A2 and restrains first of all the tendon of the flexor digitorum profundus muscle. In the area

  2. Downsized Sheath-Core Conducting Fibers for Weavable Superelastic Wires, Biosensors, Supercapacitors, and Strain Sensors.

    PubMed

    Wang, Hongyan; Liu, Zunfeng; Ding, Jianning; Lepró, Xavier; Fang, Shaoli; Jiang, Nan; Yuan, Ninyi; Wang, Run; Yin, Qu; Lv, Wei; Liu, Zhongsheng; Zhang, Mei; Ovalle-Robles, Raquel; Inoue, Kanzan; Yin, Shougen; Baughman, Ray H

    2016-07-01

    Hair-like-diameter superelastic conducting fibers, comprising a buckled carbon nanotube sheath on a rubber core, are fabricated, characterized, and deployed as weavable wires, biosensors, supercapacitors, and strain sensors. These downsized sheath-core fibers provide the demonstrated basis for glucose sensors, supercapacitors, and electrical interconnects whose performance is undegraded by giant strain, as well as ultrafast strain sensors that exploit strain-dependent capacitance changes. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Anisotropic emission of neutral atoms: evidence of an anisotropic Rydberg sheath in nanoplasma

    NASA Astrophysics Data System (ADS)

    Rajeev, R.; Madhu Trivikram, T.; Rishad, K. P. M.; Krishnamurthy, M.

    2015-02-01

    Intense laser-produced plasma is a complex amalgam of ions, electrons and atoms both in ground and excited states. Little is known about the spatial composition of the excited states that are an integral part of most gaseous or cluster plasma. In cluster-plasma, Rydberg excitations change the charge composition of the ions through charge transfer reactions and shape the angular distributions. Here, we demonstrate a non-invasive technique that reveals the anisotropic Rydberg excited cluster sheath by measuring anisotropy in fast neutral atoms. The sheath is stronger in the direction of light polarization and the enhanced charge transfer by the excited clusters results in larger neutralization.

  4. Is the leaf bundle sheath a "smart flux valve" for K+ nutrition?

    PubMed

    Wigoda, Noa; Moshelion, Menachem; Moran, Nava

    2014-05-15

    Evidence has started to accumulate that the bundle sheath regulates the passage of water, minerals and metabolites between the mesophyll and the conducting vessels of xylem and phloem within the leaf veins which it envelops. Although potassium (K(+)) nutrition has been studied for several decades, and much is known about the uptake and recirculation of K(+) within the plant, the potential regulatory role of bundle sheath with regard to K(+) fluxes has just begun to be addressed. Here we have collected some facts and ideas about these processes.

  5. Parameters of a collisional radio-frequency sheath and dust characteristics resulting from the microparticle levitation

    SciTech Connect

    Yaroshenko, V. V.; Antonova, T.; Thomas, H. M.; Morfill, G. E.

    2009-10-15

    The screening length, the time-average electric field, and the particle charge as well as the local vertical gradients of these quantities are determined experimentally within a sheath of a capacitively coupled rf, 13.56 MHz, discharge at enhanced argon gas pressures of 30, 55, and 100 Pa. The parameters are derived directly from comparative measurements of levitation positions of the particles of different sizes and variations in the levitation heights caused by formation of new dust layers. The electrostatic effect of the horizontally extended dust layers on the sheath electric field is investigated.

  6. Malfunction of dialysis catheters: management of fibrin sheath and related problems.

    PubMed

    Faintuch, Salao; Salazar, G M M

    2008-09-01

    Suitable central venous access for hemodialysis is frequently required in patients with end-stage renal disease, whenever an arteriovenous fistula or peritoneal dialysis fails or is not a possibility. Ultimately, long-term dialysis via central access may result in dysfunctional catheter with problems such as malpositioning of catheter tip, fibrin sheath formation, thrombosis, infection, and bleeding. The role of interventional radiology is to deliver appropriate treatment to maintain patent and functional access, while minimizing the risk of venous occlusive disease. This article aims at describing different techniques and approaches for management of fibrin sheath associated with malfunctioning tunneled dialysis catheters, as well as to provide scientific evidence from the current literature.

  7. A dynamic analysis of the magnetized plasma sheath in a collisionless scenario with ion sources

    NASA Astrophysics Data System (ADS)

    Adhikari, S.; Moulick, R.; Goswami, K. S.

    2017-08-01

    The influence of the forces that control the ion dynamics inside a magnetized plasma sheath under collisionless conditions is analyzed. Considering the ionization, the effects of the variation of field strength and the inclination angle on the force fields inside the sheath are studied. The pitch length and pitch angle for the particle velocity fields are also calculated and have been found to vary widely with the inclination angle and the strength of the magnetic field. The role of the Lorentz force and energy acquired by the ions while moving towards the wall is highlighted. A comparison between two different ion sources has also been foregrounded.

  8. Extensor tendon sheath fistula formation as a complication of wrist arthroscopy.

    PubMed

    Shirley, Denise S L; Mullet, Hannan; Stanley, John K

    2008-11-01

    The indications and applications for wrist arthroscopy continue to expand as new techniques and instrumentation evolve. Wrist arthroscopy is now the gold standard investigation for chronic wrist pain before definitive surgery. Although complications are uncommon, they may include infection, neuroma formation, tendon injury, dorsal skin slough, tourniquet neurapraxia, and reflex sympathetic dystrophy. We describe extensor tendon sheath fistula formation arising from the 3/4 portal after diagnostic wrist arthroscopy and our management in this novel case. The formation of a patent communication between the radiocarpal joint and the tendon sheath permitting the collection of synovial fluid has not previously been described.

  9. Reconstruction with the use of a sheath of fine stainless steel wire mesh.

    PubMed

    Dias, A D

    1982-10-01

    This paper describes the use of stainless steel wire mesh as the basic material in fabricating a sheath to be inserted as a surgical implant. This sheath can be moulded into various shapes and sizes by hand at the time of operation. It has been used for reconstruction in various areas. It is inexpensive and its range of application appears to be considerable. It has been used to date in 16 patients and two cases have now been followed up for over one year.

  10. Simulation of arc-electrode interaction using sheath modelling in SF6 circuit-breakers

    NASA Astrophysics Data System (ADS)

    Maruzewski, P.; Martin, A.; Reggio, M.; Trépanier, J.-Y.

    2002-05-01

    The transition layer, or sheath, located at the interface between the electrode and the electric arc plasma in circuit-breaker arcs is modelled and integrated into software for the simulation of arcs. The sheath model includes the equation of the continuity of electrons, the generalized Ohm's law and the equation of conservation of total energy. The latter equation takes into account Joule heating, the radiation from the arc and phenomena on the surface of the electrode such as thermionic and radiative cooling by thermal emission. The resulting arc model can predict electrode and arc temperatures simultaneously.

  11. Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres

    SciTech Connect

    Sheridan, T. E.; Katschke, M. R.; Wells, K. D.

    2007-02-15

    A method for measuring the time-averaged vertical electric field and its gradient in the plasma sheath using clusters with n=2 or 3 floating microspheres of known mass is described. The particle charge q is found by determining the ratio of the breathing frequency to the center-of-mass frequency for horizontal (in-plane) oscillations. The electric field at the position of the particles is then calculated using the measured charge-to-mass ratio, and the electric-field gradient is determined from the vertical resonance frequency. The Debye length is also found. Experimental results are in agreement with a simple sheath model.

  12. The Presence of Turbulent and Ordered Local Structure within the ICME Shock-sheath and Its Contribution to Forbush Decrease

    NASA Astrophysics Data System (ADS)

    Shaikh, Zubair; Raghav, Anil; Bhaskar, Ankush

    2017-08-01

    The transient interplanetary disturbances evoke short-time cosmic-ray flux decrease, which is known as Forbush decrease. The traditional model and understanding of Forbush decrease suggest that the sub-structure of an interplanetary counterpart of coronal mass ejection (ICME) independently contributes to cosmic-ray flux decrease. These sub-structures, shock-sheath, and magnetic cloud (MC) manifest as classical two-step Forbush decrease. The recent work by Raghav et al. has shown multi-step decreases and recoveries within the shock-sheath. However, this cannot be explained by the ideal shock-sheath barrier model. Furthermore, they suggested that local structures within the ICME’s sub-structure (MC and shock-sheath) could explain this deviation of the FD profile from the classical FD. Therefore, the present study attempts to investigate the cause of multi-step cosmic-ray flux decrease and respective recovery within the shock-sheath in detail. A 3D-hodogram method is utilized to obtain more details regarding the local structures within the shock-sheath. This method unambiguously suggests the formation of small-scale local structures within the ICME (shock-sheath and even in MC). Moreover, the method could differentiate the turbulent and ordered interplanetary magnetic field (IMF) regions within the sub-structures of ICME. The study explicitly suggests that the turbulent and ordered IMF regions within the shock-sheath do influence cosmic-ray variations differently.

  13. Investigation of the sheath formation in a dusty plasma containing energetic electrons and nano-size dust grains

    SciTech Connect

    Foroutan, G.; Akhoundi, A.

    2012-10-15

    Numerical simulations of the stationary multi-fluid equations are used to study the structure of a dusty plasma sheath in the presence of a beam of energetic electrons. It is found that even a small number of energetic electrons can strongly modify the sheath parameters, specially the sheath thickness. Depending on the magnitude of the beam flux, two different regimes of sheath thickness can be recognized; At small beam fluxes, the sheath is in the regime of thin sheath and its thickness grows linearly with the beam flux. As the beam flux increases, at a certain beam energy or beam number density, the sheath demonstrates a sharp transition to the regime of thick sheath where the width is almost three times larger. The beam parameters corresponding to the transition between the two regimes depend on the parameters of the background plasma. The beam transition energy increases with the electron temperature and dust number density while decreases with the dust radius. On the other hand, the beam transition number density is a non-monotonic function of the background plasma number density. The localization of dust particles above the substrate is intensified by the increase in the beam number density.

  14. The narrow sheath duplicate genes: sectors of dual aneuploidy reveal ancestrally conserved gene functions during maize leaf development.

    PubMed Central

    Scanlon, M J; Chen, K D; McKnight CC, I V

    2000-01-01

    The narrow sheath mutant of maize displays a leaf and plant stature phenotype controlled by the duplicate factor mutations narrow sheath1 and narrow sheath2. Mutant leaves fail to develop a lateral domain that includes the leaf margins. Genetic data are presented to show that the narrow sheath mutations map to duplicated chromosomal regions, reflecting an ancestral duplication of the maize genome. Genetic and cytogenetic evidence indicates that the original mutation at narrow sheath2 is associated with a chromosomal inversion on the long arm of chromosome 4. Meristematic sectors of dual aneuploidy were generated, producing plants genetically mosaic for NARROW SHEATH function. These mosaic plants exhibited characteristic half-plant phenotypes, in which leaves from one side of the plant were of nonmutant morphology and leaves from the opposite side were of narrow sheath mutant phenotype. The data suggest that the narrow sheath duplicate genes may perform ancestrally conserved, redundant functions in the development of a lateral domain in the maize leaf. PMID:10880496

  15. Numerical investigation of fast-wave propagation and radio-frequency sheath interaction with a shaped tokamak wall

    SciTech Connect

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2015-07-15

    Interactions between propagating fast waves and radio-frequency (RF) sheaths in the ion cyclotron range of frequencies are numerically investigated based on a cold fluid plasma model coupled with a sheath boundary condition. In this two-dimensional study, the capability of the finite element code rfSOL, which was developed in previous numerical work, is extended to analyze self-consistent RF sheath-plasma interaction problems in a tokamak with a non-circular cross-section. It is found that a large sheath voltage is generated near the edges of the limiter-shaped deformation as a result of the conversion from fast to slow waves on the sheaths. The sheath voltage associated with this conversion is particularly significant in the localized region where the contact angle between the magnetic field line and the conducting wall varies rapidly along the curved sheath surface, which is consistent with the results in previous one-dimensional theoretical work. The dependences of the RF sheaths on various parameters in plasma such as the toroidal wavenumber, edge plasma density, and the degree of the RF wave absorption in the core region are also examined in detail.

  16. Pressure gradients along whole culms and leaf sheaths, and other aspects of humidity-induced gas transport in Phragmites australis.

    PubMed

    Afreen, F; Zobayed, S M A; Armstrong, J; Armstrong, W

    2007-01-01

    Emergent aquatic macrophytes growing in waterlogged anaerobic sediments overlain by deep water require particularly efficient ventilating systems. In Phragmites australis (Cav.) Trin. ex Steud, pressurized gas flows, generated by humidity-induced diffusion of air into leaf sheaths, enhance oxygen transport to below-ground parts and aid in the removal of respiratory CO2 and sediment-generated CO2 and methane. Although modelling and flow measurements have pointed to the probable involvement of all leaf sheaths in the flow process and the development of pressure gradients along the whole lengths of living culm and leaf sheaths, direct measurements of pressure gradients have never been reported. The aim of this study was to search for pressure gradient development in Phragmites culms and leaf sheaths and to determine their magnitudes and distribution. In addition, dynamic (with gas flow) and static pressures (no flow condition) and their relationship to flows, leaf sheath areas, and living-to-dead culm ratios were further investigated. Dynamic pressures (DeltaPd) recorded in the pith cavities of intact (non-excised) leafy culms, pneumatically isolated from the below-ground parts and venting through an artificial bore-hole near the base, revealed a curvilinear gradient of pressure 'asymptoting' towards the tips of the culms. Similarly, DeltaPd in upper and lower parts of leaf sheaths increased with distance from the base of the culm, with values in the upper parts always being greater. Curvilinear gradients of pressure were also found along pneumatically isolated individual leaf sheaths, but radial channels linking the leaf sheath aerenchyma with the pith cavity of the culm appeared to offer little resistance to flow. In keeping with predictions, static pressure differentials (DeltaPs) achieved in intact and excised culms and single leaf sheaths on intact culms proved to be relatively independent of leaf sheath area, whereas the potential for developing convective flows

  17. Fine structure of modal focusing effect in a three dimensional plasma-sheath-lens formed by disk electrodes

    SciTech Connect

    Stamate, Eugen; Yamaguchi, Masahito

    2015-08-31

    Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the geometrical structure of the plasma-sheath-lens and plasma parameters. The positive and negative ion kinetics within the plasma-sheath-lens are investigated both experimentally and theoretically and a modal focusing ring is identified on the surface of disk electrodes. The focusing ring is very sensitive to the sheath thickness and can be used to monitor very small changes in plasma parameters. Three dimensional simulations are found to be in very good agreement with experiments.

  18. Modal focusing effect of positive and negative ions by a three-dimensional plasma-sheath lens.

    PubMed

    Stamate, E; Sugai, H

    2005-04-01

    A complex focusing effect of positive and negative ions caused by the sheath forming to biased electrodes that interface insulators has been found by solving in three dimensions the potential distribution and ion kinetics within the sheath. Thus, intrinsically correlated with the sheath shape, certain electrical charges are focused on the surface, forming well defined patterns named modal lines and modal spots. Their superposition to the previously reported discrete focusing leads to a total flux that represents a "fingerprint" of the entire sheath on the electrode surface. The ion flux pattern is developed experimentally on the surface of square and octagonal electrodes exposed to Ar/SF(6) and CF4 plasmas. Present results are of high potential importance for fundamental studies concerning sheath formation and charge kinetics and also in a wide range of plasma applications.

  19. [Microstructure comparison of jaw sheaths between the Megophryid tadpoles (Amphibia, Anura) by the technology of electron microscope].

    PubMed

    Li, Cheng; Dong, Zhao-xiong; Wang, Yue-zhao

    2010-10-01

    The jaw sheaths morphology of eight megophryid larvae were examined using scanning electron microscope. The morphology of jaw sheaths of Leptobrachiinae and Leptolalaginae larvae was similar. Their jaw sheaths were U-shaped and strong keratinized, the serrations were pyramidal, with broad-based and short pointed. While the jaw sheaths of Megophryinae larvae were less curved and weak keratinized, the serrations were ivory-shaped, with narrow-based and long pointed. It has been found that the relationship between serration's diameter and density was negatively correlated, the changing trend reflected the functional significance of serrations. These distinctions among the jaw sheaths of tadpoles most could be related to their specific ecological habits and to their dietary specializations.

  20. Development of a Sheathed Miniature Aerothermal Reentry Thermocouple for Thermal Protection System Materials

    NASA Technical Reports Server (NTRS)

    Martinez, Edward R.; Weber, Carissa Tudryn; Oishi, Tomo; Santos, Jose; Mach, Joseph

    2011-01-01

    The Sheathed Miniature Aerothermal Reentry Thermocouple is a micro-miniature thermocouple for high temperature measurement in extreme environments. It is available for use in Thermal Protection System materials for ground testing and flight. This paper discusses the heritage, and design of the instrument. Experimental and analytical methods used to verify its performance and limitations are described.